Communication system, transmission device, reception device, communication method, program, and communication cable

ABSTRACT

The present invention relates to a communication system, a transmission device, a reception device, a communication method, a program, and a communication cable, whereby high-speed communication can be executed while maintaining compatibility. In the event that an HDMI(R) source  71  and an HDMI(R) sink  72  execute two-way IP communication using a CEC line  84  and a signal line  141 , a switching control unit  121  controls a switch  133  to select a partial signal making up the differential signal from a conversion unit  131  at the time of transmitting data, and controls the switch  133  to select a partial signal making up a differential signal from a receiver  82  at the time of transmitting data, and in the case of executing two-way communication using the CEC line  84  alone, the switching control unit  121  controls the switch  133  to select the CEC signal from the HDMI(R) source  71  or receiver  82  with the switch  133 . The present invention may be applied to HDMI(R), for example.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.12/452,184, filed on Apr. 7, 2010 which is a national phase entry under35 U.S.C. §371 of International Application No. PCT/JP2008/061604 filedJun. 26, 2008, published on Dec. 31, 2008 as WO 2009/001880 A1, whichclaims priority from Japanese Patent Application No. JP 2007-168176filed in the Japanese Patent Office on Jun. 26, 2007, all of which areincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a communication system, a transmissiondevice, a reception device, a communication method, a program, and acommunication cable, and more specifically, it relates to acommunication system, a transmission device, a reception device, acommunication method, a program, and a communication cable, wherebyhigh-speed communication can be executed while maintaining compatibilitywith a communication interface, for example, such as an HDMI (HighDefinition Multimedia Interface)(R) whereby the pixel data of anuncompressed image can be transmitted in one direction at high speed.

BACKGROUND ART

In recent years, for example, HDMI(R) is becoming widespread as acommunication interface wherein a digital television signal, i.e., thepixel data of an uncompressed (baseband) image, and audio dataaccompanying the image thereof are transmitted from, e.g., a DVD(Digital Versatile Disc) recorder, set top box, or other AV (AudioVisual) source to a television receiver, a projector, or other displaydevice at high speed.

With regard to HDMI(R), a TMDS (Transition Minimized DifferentialSignaling) channel for transmitting pixel data and audio data from anHDMI(R) source to an HDMI(R) sink in one direction at high speed, a CECline (Consumer Electronics Control Line) for executing two-waycommunication between an HDMI(R) source and an HDMI(R) sink, and soforth are stipulated in the HDMI standard.

For example, such as shown in FIG. 1, a digital television receiver 11,and an AV amplifier 12 are connected with an HDMI cable 13 conforming toHDMI(R), thereby enabling the high-speed transmission of pixel data andaudio data.

In FIG. 1, a digital television receiver 11, an AV amplifier 12, and aplayback device 14 are installed in a living room situated to the leftside in the drawing of a user's home, and between the digital televisionreceiver 11 and the AV amplifier 12, and between the AV amplifier 12 andthe playback device 14 are connected with an HDMI(R) cable 13, and anHDMI(R) cable 15.

Also, a hub 16 is installed in the living room, and the televisionreceiver 11 and the playback device 14 are connected to the hub 16 usinga LAN (Local Area Network) cable 17 and a LAN cable 18. Further, in thedrawing, a digital television receiver 19 is installed in a bedroomsituated to the right side of the living room, and the digitaltelevision receiver 19 is connected to the hub 16 via a LAN cable 20.

For example, in the case that a content recorded in the playback device14 is played, and an image is displayed on the digital televisionreceiver 11, the playback device 14 decodes the pixel data and audiodata for playing the content, and supplies the uncompressed pixel dataand audio data obtained as a result thereof to the digital televisionreceiver 11 via the HDMI(R) cable 15, AV amplifier 12, and HDMI(R) cable13. Subsequently, the digital television receiver 11 displays an image,or outputs audio based on the pixel data and audio data supplied fromthe playback device 14.

Also, in the case that a content recorded in the playback device 14 isplayed, and an image is displayed on the digital television receiver 11and the digital television receiver 19 simultaneously, the playbackdevice supplies the compressed pixel data and audio data for playing thecontent to the digital television receiver 11 via the LAN cable 18, hub16, and LAN cable 17, and also supplies those to the digital televisionreceiver 19 via the LAN cable 18, hub 16, and LAN cable 20.

Subsequently, the digital television receiver 11 and digital televisionreceiver 19 decode the pixel data and audio data supplied from theplayback device 14, and displays an image or outputs audio based on theuncompressed pixel data and audio data obtained as a result thereof.

Further, in the case that the digital television receiver 11 hasreceived pixel data and audio data for playing a program on air ontelevision, in the event that the received audio data is, for example,5.1-channel surround audio data or the like, and the digital televisionreceiver 11 has difficulty in decoding the received audio data, thetelevision receiver 11 converts the audio data into an optical signal,and transmits this to the AV amplifier 12.

The AV amplifier 12 receives the optical signal transmitted from thedigital television receiver 11 to subject this to photoelectricconversion, and decodes the audio data thus obtained. Subsequently, theAV amplifier 12 amplifies the decoded uncompressed audio data asappropriate, and plays the audio using a surround speaker connected tothe AV amplifier 12. Thus, the digital television receiver 11 decodesthe received pixel data, displays the image based on the decoded pixeldata, and plays the 5.1-channel surround program by outputting the audiousing the AV amplifier 12 based on the audio data supplied to the AVamplifier 12.

Incidentally, with regard to HDMI(R), a device has been proposed whereinwhen transmitting pixel data and audio data from an HDMI(R) source to anHDMI(R) sink, discarded data is muted by turning on/off transmission ofdata (e.g., see Patent Document 1).

Further, with regard to HDMI(R), a device has been proposed wherein, ofmultiple HDMI(R) sinks, pixel data and audio data can be output to adesired HDMI(R) sink without switching a cable for connecting an HDMI(R)source and an HDMI(R) sink by switching a terminal for outputting pixeldata and audio data using a changeover switch (e.g., see Patent Document2).

-   Patent Document 1: Japanese Unexamined Patent Application    Publication No. 2005-57714-   Patent Document 2: Japanese Unexamined Patent Application    Publication No. 2006-19948

DISCLOSURE OF INVENTION Technical Problem

As described above, with HDMI(R), pixel data and audio data can betransmitted from an HDMI(R) source to an HDMI(R) sink in one directionat high speed, and also two-way communication can be executed between anHDMI(R) source and an HDMI(R) sink.

Note however, the transmission rate of two-way communication that can beexecuted with the current HDMI(R) is several hundreds bps, andaccordingly, two-way communication such as two-way IP (InternetProtocol) communication or the like has difficulty in being executedbetween an HDMI(R) source and an HDMI(R) sink at high speed.

Therefore, in the case of executing two-way IP communication withHDMI(R) including the devices described in Patent Document 1 and PatentDocument 2, the data amount of data to be transmitted with IPcommunication is restricted. Also, upon transmitting data having greatdata amount using IP communication, great time delay is caused.Accordingly, for example, it has been difficult for an application usedfor transmitting data having great data amount such as a compressedimage bi-directionally, or an application for requesting a high-speedresponse to employ HDMI(R).

Therefore, for example, a method can be conceived wherein a dedicatedpin for two-way high-speed IP communication is provided to theconnectors for HDMI(R) of an HDMI(R) source and an HDMI(R) sink, andtwo-way IP communication is executed at high speed using the dedicatedpins thereof.

Note however, providing a dedicated pin to the connector of the currentHDMI(R) reduces compatibility as to the current HDMI(R).

The present invention has been made in the light of such a situation,and the object thereof is to enable a communication interface capable oftransmitting pixel data of an uncompressed image in one direction athigh speed, such as HDMI(R) for example, to execute high-speed two-waycommunication while maintaining compatibility.

Technical Solution

A communication system according to a first aspect of the presentinvention is a communication system including: a transmission deviceconfigured to transmit pixel data of one screen worth of an uncompressedimage to a reception device in one direction within a valid imagesection that is a section obtained by removing a horizontal retracesection and a vertical retrace section from a section from one verticalsynchronizing signal to the next vertical synchronizing signal, using afirst differential signal; and a reception device configured to receivethe first differential signal transmitted from the transmission device;with the transmission device including first conversion means configuredto convert data different from the pixel data, which is data to betransmitted, into a second differential signal made up of a firstpartial signal and a second partial signal, transmit the first partialsignal to the reception device via a first signal line, and also outputthe second partial signal, first selecting means configured to selectone of a transmission signal that is a signal relating to control, andthe second partial signal output from the first conversion means, andtransmit the selected signal to the reception device via a second signalline, first control means configured to control, in the case oftransmitting the transmission signal to the reception device, the firstselecting means so as to select the transmission signal, and in the caseof transmitting the second differential signal to the reception device,to control the first selecting means so as to select the second partialsignal, and first decoding means configured to receive a thirddifferential signal transmitted from the reception device, and decodethis to the original data; and with the reception device includingsecond conversion means configured to convert data different from thepixel data, which is data to be transmitted, into the third differentialsignal, and transmit this to the transmission device, second decodingmeans configured to receive the second differential signal transmittedfrom the transmission device, and decode this to the original data,second selecting means configured to select one of the transmissionsignal and the second partial signal, and second control meansconfigured to control, in the case of receiving the transmission signal,the second selecting means so as to select and receive the transmissionsignal, and in the case of receiving the second differential signal, tocontrol the second selecting means so as to select the second partialsignal, and the second decoding means so as to receive the secondpartial signal.

A communication method according to the first aspect of the presentinvention is a communication method for a communication system includinga transmission device configured to transmit pixel data of one screenworth of an uncompressed image to a reception device in one directionwithin a valid image section that is a section obtained by removing ahorizontal retrace section and a vertical retrace section from a sectionfrom one vertical synchronizing signal to the next verticalsynchronizing signal, using a first differential signal, and a receptiondevice configured to receive the first differential signal transmittedfrom the transmission device; with the transmission device includingfirst conversion means configured to convert data different from thepixel data, which is data to be transmitted, into a second differentialsignal made up of a first partial signal and a second partial signal,transmit the first partial signal to the reception device via a firstsignal line, and also output the second partial signal, first selectingmeans configured to select one of a transmission signal that is a signalrelating to control, and the second partial signal output from the firstconversion means, and first decoding means configured to receive a thirddifferential signal transmitted from the reception device, and decodethis to the original data; with the reception device including secondconversion means configured to convert data different from the pixeldata, which is data to be transmitted, into the third differentialsignal, and transmit this to the transmission device, second decodingmeans configured to receive the second differential signal transmittedfrom the transmission device, and decode this to the original data, andsecond selecting means configured to select one of the transmissionsignal and the second partial signal; and with the communication methodincluding the steps of: controlling, in the case of transmitting thetransmission signal to the reception device, the first selecting meansso as to select the transmission signal, and in the case of transmittingthe second differential signal to the reception device, controlling thefirst selecting means so as to select the second partial signal,controlling, in the case of the receiving device receiving thetransmission signal, the second selecting means so as to select andreceive the transmission signal, and in the case of the receiving devicereceiving the second differential signal, controlling the secondselecting means so as to select the second partial signal, and thesecond decoding means so as to receive the second partial signal.

With the first aspect of the present invention, with the transmissiondevice, data different from pixel data, which is data to be transmitted,is converted into a second differential signal made up of a firstpartial signal and a second partial signal, the first partial signal istransmitted to the reception device via a first line, and also saidsecond partial signal is output, one of a transmission signal that is asignal relating to control, and said output second partial signal isselected, and the selected signal is transmitted to the reception devicevia a second signal line. Here, in the case of transmitting thetransmission signal to the reception device, the transmission signal iscontrolled so as to be selected, and in the case of transmitting thesecond differential signal to the reception device, the second partialsignal is controlled so as to be selected. Also, the third differentialsignal transmitted from said reception device is received, and isdecoded to the original data.

On the other hand, with the reception device, data different from thepixel data, which is data to be transmitted, is converted into the thirddifferential signal, and is transmitted to the transmission device, andthe second differential signal transmitted from the transmission deviceis received, and is decoded to the original data, and one of thetransmission signal and the second partial signal is selected. Here, inthe case of receiving the transmission signal, the transmission signalis controlled so as to be selected and received, and in the case ofreceiving the second differential signal, the second partial signal iscontrolled so as to be selected and received.

A transmission device according to a second aspect of the presentinvention is a transmission device configured to transmit pixel data ofone screen worth of an uncompressed image to a reception device in onedirection within a valid image section that is a section obtained byremoving a horizontal retrace section and a vertical retrace sectionfrom a section from one vertical synchronizing signal to the nextvertical synchronizing signal, using a first differential signal,including: conversion means configured to convert data different fromthe pixel data, which is data to be transmitted, into a seconddifferential signal made up of a first partial signal and a secondpartial signal, transmit the first partial signal to the receptiondevice via a first signal line, and also output the second partialsignal; first selecting means configured to select one of a firsttransmission signal that is a signal relating to control, and the secondpartial signal output from the conversion means, and transmit theselected signal to the reception device via a second signal line; firstcontrol means configured to control, in the case of transmitting thefirst transmission signal to the reception device, the first selectingmeans so as to select the first transmission signal, and in the case oftransmitting the second differential signal to the reception device, tocontrol the first selecting means so as to select the second partialsignal; and decoding means configured to receive a third differentialsignal made up of a third partial signal and a fourth partial signal,transmitted from the reception device, and decode this to the originaldata.

The decoding means may be controlled to receive the third differentialsignal made up of the third partial signal transmitted via the secondsignal line, and the fourth partial signal transmitted via the firstsignal line; with the first selecting means being controlled to selectthe second partial signal or the third partial signal, or the firsttransmission signal; and with the first control means being controlledto cause first selecting means to select the third partial signal, andthe decoding means to receive the third partial signal, in the case ofreceiving the third differential signal.

The first selecting means may select the second partial signal or thethird partial signal, or the first transmission signal, or a receptionsignal that is a signal relating to control, transmitted from thereception device via the second signal line, and in the case ofselecting the reception signal, receive and output the selectedreception signal.

The decoding means may receive the third differential signal made up ofthe third partial signal transmitted via a third signal line, and thefourth partial signal transmitted via a fourth signal line; with thetransmission device further including: second selecting means configuredto select one of the third partial signal, and a second transmissionsignal that is a signal relating to control, to be transmitted to thereception device; third selecting means configured to select one of thefourth partial signal, and a third transmission signal to be transmittedto the reception device; and second control means configured to control,in the case of transmitting the second transmission signal and the thirdtransmission signal to the reception device, the second selecting meansso as to select the second transmission signal and to transmit thesecond transmission signal to the reception device via the third signalline, and to control the third selecting means so as to select the thirdtransmission signal and to transmit the third transmission signal to thereception device via the fourth signal line, and in the case ofreceiving the third differential signal, control the second selectingmeans so as to select the third partial signal, and the decoding meansso as to receive this, and the third selecting means so as to select thefourth partial signal, and the decoding means so as to receive this.

The first selecting means may select the second partial signal, or thefirst transmission signal, or a first reception signal that is a signalrelating to control, transmitted from the reception device via thesecond signal line, and in the case of selecting the first receptionsignal, to receive and output the selected first reception signal; withthe second selecting means selecting the third partial signal, or thesecond transmission signal, or a second reception signal that is asignal relating to control, transmitted from the reception device viathe third signal line, and in the case of selecting the second receptionsignal, receiving and outputting the selected second reception signal.

The first transmission signal and the first reception signal may be aCEC (Consumer Electronics Control) signal that is data for control ofthe transmission device or the reception device; with the secondreception signal being E-EDID (Enhanced Extended Display IdentificationData) that is information relating to the performance of the receptiondevice, used for control; with data to be converted into the seconddifferential signal, and data obtained by decoding the thirddifferential signal being data conforming to IP (Internet Protocol);with the first control means being controlled to cause the firstselecting means to select the second partial signal after receiving thesecond reception signal; and with the second control means beingcontrolled to cause the second selecting means and the third selectingmeans to select the third partial signal and the fourth partial signalafter receiving the second reception signal.

A communication method or program according to the second aspect of thepresent invention is a communication method for a transmission device ora program causing a computer to control a transmission device, which isconfigured to transmit pixel data of one screen worth of an uncompressedimage to a reception device in one direction within a valid imagesection that is a section obtained by removing a horizontal retracesection and a vertical retrace section from a section from one verticalsynchronizing signal to the next vertical synchronizing signal, using afirst differential signal; with the transmission device includingconversion means configured to convert data different from the pixeldata, which is data to be transmitted, into a second differential signalmade up of a first partial signal and a second partial signal, transmitthe first partial signal to the reception device via a first signalline, and also output the second partial signal, selecting meansconfigured to select one of a transmission signal that is a signalrelating to control, and the second partial signal output from theconversion means, and transmit the selected signal to the receptiondevice via a second signal line, and decoding means configured toreceive a third differential signal transmitted from the receptiondevice, and decode this to the original data; with the communicationmethod including the step of controlling, in the case of transmittingthe transmission signal to the reception device, the selecting means soas to select the transmission signal, and in the case of transmittingthe second differential signal to the reception device, controlling theselecting means so as to select the second partial signal.

With the second aspect of the present invention, data different frompixel data, which is data to be transmitted, is converted into a seconddifferential signal made up of a first partial signal and a secondpartial signal, the first partial signal is transmitted to the receptiondevice via a first signal line, and also the second partial signal isoutput, one of a first transmission signal that is a signal relating tocontrol, and the output second partial signal is selected, and theselected signal is transmitted to the reception device via a secondsignal line. Here, in the case of transmitting the first transmissionsignal to the reception device, the first transmission signal iscontrolled so as to be selected, and in the case of transmitting thesecond differential signal to the reception device, the second partialsignal is controlled so as to be selected. Also, a third differentialsignal made up of a third partial signal and a fourth partial signaltransmitted from the reception device is received, and is decoded to theoriginal data.

A reception device according to a third aspect of the present inventionis a reception device configured to receive the pixel data of one screenworth of an uncompressed image to be transmitted from a transmissiondevice in one direction within a valid image section that is a sectionobtained by removing a horizontal retrace section and a vertical retracesection from a section from one vertical synchronizing signal to thenext vertical synchronizing signal, using a first differential signal,including: decoding means configured to receive a second differentialsignal made up of a first partial signal transmitted from thetransmission device via a first signal line, and a second partial signaltransmitted from the transmission device via a second signal line, anddecode this to the original data; first selecting means configured toselect one of the first partial signal, and a first reception signalthat is a signal relating to control, transmitted from the transmissiondevice via the first signal line; first control means configured tocontrol, in the case of receiving the first reception signal, the firstselecting means so as to select and receive the first reception signal,and in the case of receiving the second differential signal, to controlthe first selecting means so as to select the first partial signal, andthe decoding means so as to receive this; and conversion meansconfigured to convert data different from the pixel data, which is datato be transmitted, into a third differential signal made up of a thirdpartial signal and a fourth partial signal, and transmit this to thetransmission device.

The conversion means may be controlled to output the third partialsignal, and also transmit the fourth partial signal to the transmissiondevice via the second signal line; with the first selecting means beingcontrolled to select the first reception signal, or the first partialsignal, or the third partial signal output from the conversion means;and with the first control means being controlled to cause the firstselecting means to select the third partial signal, and transmit this tothe transmission device via the first signal line, in the case oftransmitting the third differential signal.

The first selecting means may select the first partial signal or thethird partial signal, or the first reception signal, or a transmissionsignal that is a signal relating to control, and in the case ofselecting the transmission signal, to transmit the selected transmissionsignal to the transmission device via the first signal line.

The conversion means may output the third partial signal and the fourthpartial signal; with the reception device further including: secondselecting means configured to select one of the third partial signaloutput from the conversion means, and a second reception signal that isa signal relating to control, transmitted from the transmission devicevia a third signal line; third selecting means configured to select oneof the fourth partial signal output from the conversion means, and athird reception signal transmitted from the transmission device via afourth signal line; and second control means configured to control, inthe case of receiving the second reception signal and the thirdreception signal, the second selecting means so as to select the secondreception signal so as to receive this, and also control the thirdselecting means so as to select the third reception signal so as toreceive this, and in the case of transmitting the third differentialsignal, to control the second selecting means so as to select the thirdpartial signal and transmit this to the transmission device via thethird signal line, and also to control the third selecting means so asto select the fourth partial signal and to transmit this to thetransmission device via the fourth signal line.

The first selecting means may select the first partial signal, or thefirst reception signal, or a first transmission signal that is a signalrelating to control, and in the case of selecting the first transmissionsignal, transmit the selected first transmission signal to thetransmission device via the first signal line; with the second selectingmeans selecting the third partial signal, or the second receptionsignal, or a second transmission signal that is a signal relating tocontrol, to be transmitted to the transmission device, and in the caseof selecting the second transmission signal, transmitting the selectedsecond transmission signal to the transmission device via the thirdsignal line.

A communication method or program according to the third aspect of thepresent invention is a communication method for a reception device or aprogram causing a computer to control a reception device, which isconfigured to receive the pixel data of one screen worth of anuncompressed image to be transmitted from a transmission device in onedirection within a valid image section that is a section obtained byremoving a horizontal retrace section and a vertical retrace sectionfrom a section from one vertical synchronizing signal to the nextvertical synchronizing signal, using a first differential signal, withthe reception device including decoding means configured to receive asecond differential signal made up of a first partial signal transmittedfrom the transmission device via a first signal line, and a secondpartial signal transmitted from the transmission device via a secondsignal line, and decode this to the original data, selecting meansconfigured to select one of the first partial signal, and a receptionsignal that is a signal relating to control, transmitted from thetransmission device via the first signal line, and conversion meansconfigured to convert data different from the pixel data, which is datato be transmitted, into a third differential signal, and transmit thisto the transmission device; with the communication method including thestep of: controlling, in the case of receiving the reception signal, theselecting means so as to select and receive the reception signal, and inthe case of receiving the second differential signal, controlling theselecting means so as to select the first partial signal, and thedecoding means so as to receive this.

With the third aspect of the present invention, a second differentialsignal made up of a first partial signal transmitted from thetransmission device via a first line, and a second partial signaltransmitted from the transmission device via a second signal line isreceived, and is decoded to the original data, and one of the firstpartial signal, and a first reception signal that is a signal relatingto control, transmitted from the transmission device via the firstsignal line is selected. Here, in the case of receiving the firstreception signal, the first reception signal is controlled so as to beselected and received, and in the case of receiving the seconddifferential signal, the first partial signal is controlled so as to beselected and received. Also, data different from the pixel data, whichis data to be transmitted, is converted into a third differential signalmade up of a third partial signal and a fourth partial signal, and istransmitted to the transmission device.

A communication cable according to a fourth aspect of the presentinvention is a communication cable configured to connect a transmissiondevice configured to transmit pixel data of one screen worth of anuncompressed image to a reception device in one direction within a validimage section that is a section obtained by removing a horizontalretrace section and a vertical retrace section from a section from onevertical synchronizing signal to the next vertical synchronizing signal,using a first differential signal, including first conversion meansconfigured to convert data different from the pixel data, which is datato be transmitted, into a second differential signal made up of a firstpartial signal and a second partial signal, transmit the first partialsignal to the reception device via a first signal line, and also outputthe second partial signal, first selecting means configured to selectone of a transmission signal that is a signal relating to control, andthe second partial signal output from the first conversion means, andtransmit the selected signal to the reception device via a second signalline, and first control means configured to control, in the case oftransmitting the transmission signal to the reception device, the firstselecting means so as to select the transmission signal, and in the caseof transmitting the second differential signal to the reception device,to control the first selecting means so as to select the second partialsignal, and a reception device configured to receive the firstdifferential signal transmitted from the transmission device, includingsecond conversion means configured to convert data different from thepixel data, which is data to be transmitted, into the third differentialsignal, and transmit this to the transmission device, second decodingmeans configured to receive the second differential signal transmittedfrom the transmission device, and decode this to the original data,second selecting means configured to select one of the second partialsignal and the transmission signal, and second control means configuredto control, in the case of receiving the transmission signal, the secondselecting means so as to select and receive the transmission signal, andin the case of receiving the second differential signal, to control thesecond selecting means so as to select the second partial signal, andthe second decoding means so as to receive the second partial signal,the communication cable including: the first signal line; and the secondsignal line; and wherein the first signal line and the second signalline are connected as a differential twist pair.

With the fourth aspect of the present invention, a first signal line anda second signal line are provided to a communication cable forconnecting a transmission device and a reception device, and the firstsignal line and the second signal line are connected as a differentialtwist pair.

A fifth aspect of the present invention is a communication systemincluding an interface arranged to execute data transmission of videoand audio, exchange and authentication of connected device information,communication of device control data, and LAN communication using asingle cable, including: a pair of differential transmission pathscapable of connecting connection-compatible devices; and a functionarranged to notify the connection state of the interface which hasexecuted LAN communication using two-way communication via the one pairof differential transmission paths, using the DC bias potential of atleast one of this one pair of differential transmission paths.

A sixth aspect of the present invention is a communication systemincluding an interface arranged to execute data transmission of videoand audio, exchange and authentication of connected device information,communication of device control data, and LAN communication using asingle cable, including: two pairs of differential transmission pathscapable of connecting connection-compatible devices; and a functionarranged to notify the connection state of the interface which hasexecuted LAN communication using one-way communication via the two pairsof differential transmission paths, using the DC bias potential of atleast one transmission path of the transmission paths; with at least twotransmission paths being used for communication of exchange andauthentication of connected device information in a manner time-sharingwith LAN communication.

Advantageous Effects

According to the present invention, two-way communication can beexecuted. Specifically, for example, with a communication interfacecapable of transmitting the pixel data of an uncompressed image, andaudio data accompanying the image thereof in one direction at highspeed, high-speed two-way communication can be executed whilemaintaining compatibility.

Also, according to the present invention, a circuit for LANcommunication can be formed regardless of electric standards stipulatedregarding DDC, and stable and sure LAN communication can be realizedinexpensively.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating the configuration of a common imagetransmission system.

FIG. 2 is a diagram illustrating the configuration of the imagetransmission system according to an embodiment to which the presentinvent has been applied.

FIG. 3 is a diagram illustrating a configuration example of an HDMI(R)source and an HDMI(R) sink.

FIG. 4 is a diagram illustrating the pin-out of the connector of thetype-A of HDMI(R).

FIG. 5 is a diagram illustrating the pin-out of the connector of thetype-C of HDMI(R).

FIG. 6 is a diagram illustrating a more detailed configuration exampleof the HDMI(R) source and the HDMI(R) sink.

FIG. 7 is a diagram illustrating another more detailed configurationexample of the HDMI(R) source and the HDMI(R) sink.

FIG. 8 is a diagram illustrating the data structure of E-EDID.

FIG. 9 is a diagram illustrating the data structure of Vender Specific.

FIG. 10 is a flowchart for describing communication processing by theHDMI(R) source.

FIG. 11 is a flowchart for describing communication processing by theHDMI(R) sink.

FIG. 12 is a flowchart for describing communication processing by theHDMI(R) source.

FIG. 13 is a flowchart for describing communication processing by theHDMI(R) sink.

FIG. 14 is a diagram illustrating another more detailed configurationexample of the HDMI(R) source and the HDMI(R) sink.

FIG. 15 is a flowchart for describing communication processing by theHDMI(R) source.

FIG. 16 is a flowchart for describing communication processing by theHDMI(R) sink.

FIG. 17 is a block diagram illustrating a configuration example of anembodiment of a computer to which the present invention has beenapplied.

FIG. 18 is a circuit diagram illustrating a first configuration exampleof a communication system of which the interface connection state isnotified with the DC bias potential of at least one of transmissionpaths.

FIG. 19 is a diagram illustrating a configuration example of a system inthe case of implementing Ethernet (Registered Trademark) (Ethernet(Registered Trademark)).

FIG. 20 is a circuit diagram illustrating a second configuration exampleof a communication system to which the connection state of an interfaceis notified with the DC bias potential of at least one of transmissionpaths.

FIG. 21 is a diagram illustrating two-way communication waveforms withthe communication system of the configuration example.

FIG. 22 is a diagram illustrating a system including multiple devices tobe connected by using HDMI and Ethernet (Registered Trademark) together.

FIG. 23 is a diagram illustrating HDMI VSDB.

FIG. 24 is a diagram illustrating CEC and DDC connections.

FIG. 25 is a diagram illustrating HDMI cluster.

FIG. 26 is a diagram illustrating HDMI cluster.

FIG. 27 is a diagram illustrating logical addresses.

FIG. 28 is a diagram for describing logical address allocation.

FIG. 29 is a diagram for describing a method for determining an IPaddress.

FIG. 30 is a diagram for describing a terminal provided with a device.

FIG. 31 is a diagram for describing a method for determining an IPaddress.

FIG. 32 is a diagram for describing a method for determining an IPaddress.

FIG. 33 is a diagram for describing a method for determining an IPaddress.

FIG. 34 is a diagram for describing a method for determining an IPaddress.

FIG. 35 is a diagram for describing connection between devices by aneHDMI cable or LAN cable.

FIG. 36 is a flowchart for describing switching processing.

FIG. 37 is a diagram illustrating the configuration of a conversionadaptor.

FIG. 38 is a diagram illustrating the configuration of a device to whicha switch for switching a connector is provided.

FIG. 39 is a diagram illustrating an example of a LAN connector and anHDMI connector provided to the device.

FIG. 40 is a diagram illustrating the configuration of the device.

EXPLANATION OF REFERENCE NUMERALS

35 HDMI(R) cable, 71 HDMI(R) source, 72 HDMI(R) sink, 81 transmitter, 82receiver, 83 DDC, 84 CEC line, 85 EDIDROM, 121 switching control unit,124 switching control unit, 131 switch, 132 decoding unit, 133 switch,134 conversion unit, 135 switch, 136 decoding unit, 141 signal line, 171switching control unit, 172 switching control unit, 181 switch, 182switch, 183 decoding unit, 184 conversion unit, 185 switch, 186 switch,191 SDA line, 192 SCL line, 400 communication system, 401 LAN functionexpansion HDMI(EH) source device, 411 LAN signal transmission circuit,12 terminating resistor, 413 and 414 AC connection capacitances, 415 LANsignal reception circuit, 416 subtracting circuit, 421 pull-up resistor,422 resistor, 423 capacitance, 424 comparator, 431 pull-down resistor,432 resistor, 433 capacitance, 434 comparator, 402 EH sink device, 441LAN signal transmission circuit, 442 terminating resistor, 443 and 444AC connection capacitances, 445 LAN signal reception circuit, 446subtracting circuit, 451 pull-down resistor, 452 resistor, 453capacitance, 454 comparator, 461 choke coil, 462 and 463 resistors, 403EH cable, 501 reserved line, 502 HPD line, 511, 512 source sideterminal, 521 and 522 sink side terminals, 600 communication system, 601LAN function expansion HDMI(EH) source device, 611 LAN signaltransmission circuit, 612 and 613 terminating resistors, 614 through 617AC connection capacitances, 618 LAN signal reception circuit, 620inverter, 621 resistor, 622 resistor, 623 capacitance, 624 comparator,631 pull-down resistor, 632 resistor, 633 capacitance, 634 comparator,640 NOR gate, 641 through 644 analog switches, 645 inverter, 646 and 647analog switches, 651 and 652 DDC transceivers, 653 and 654 pull-downresistors, 602 EH sink device, 661 LAN signal transmission circuit, 662and 663 terminating resistors, 664 through 667 AC connectioncapacitances, 668 LAN signal reception circuit, 671 pull-down resistor,672 resistor, 673 capacitance, 674 comparator, 681 choke coil, 682, 683resistor, 691 through 694 analog switches, 695 inverter, 696 and 697analog switches, 701 and 702 DDC transceivers, 703 and 704 pull-upresistors, 603 EH cable, 801 reserved line, 802 HPD line, 803 SCL line,804 SDA line, 811 through 814 source side terminals, 821 through 824sink side terminals, 901 device, 911 HDMI terminal, 912 Ethernet(Registered Trademark) terminal, 913 Ethernet (Registered Trademark)terminal, 914 HDMI terminal, 915 Ethernet (Registered Trademark)terminal, 1001 device, 1102 HDMI terminal, 1103 Ethernet (RegisteredTrademark) terminal, 1104 HDMI terminal, 1105 Ethernet (RegisteredTrademark) terminal, 1106 Ethernet (Registered Trademark) terminal, 1131conversion adaptor, 1161 network controller, 1162 network controller,1164 switch, 1165 HDMI connector, 1166 LAN connector, 1191 LANconnector, 1192 HDMI connector, 1211 LAN connector, 1212 HDMI connector,1213 network controller, 1216 network controller

BEST MODES FOR CARRYING OUT THE INVENTION

[First Embodiment] Embodiments to which the present invention has beenapplied will be described below with reference to the drawings.

FIG. 2 is a diagram illustrating the configuration of an imagetransmission system according to an embodiment to which the presentinvent has been applied.

The image transmission system is configured of a digital televisionreceiver 31, an amplifier 32, a playback device 33, and a digitaltelevision receiver 34, and between the digital television receiver 31and the amplifier 32, and between the amplifier 32 and the playbackdevice 33 are connected with an HDMI(R) cable 35 and an HDMI(R) cable 36which are communication cables conforming to HDMI(R). Also, between thedigital television receiver 31 and the digital television receiver 34 isconnected with a LAN cable 37 for LAN such as Ethernet (RegisteredTrademark) or the like.

With the example in FIG. 2, the digital television receiver 31,amplifier 32, and playback device 33 are installed in a living roomsituated to the left side in the drawing of a user's home, and thedigital television receiver 34 is installed in a bedroom situated to theright side of the living room.

The playback device 33, which is made up of, for example, a DVD player,hard disk recorder, or the like, decodes pixel data and audio data forplaying a content, and supplies uncompressed pixel data and audio dataobtained as a result thereof to the amplifier 32 via the HDMI(R) cable36.

The amplifier 32, which is made up of, for example, an AV amplifier orthe like, receives supply of pixel data and audio data from the playbackdevice 33, and amplifies the supplied audio data as appropriate. Also,the amplifier 32 supplies the audio data and pixel data supplied fromthe playback device 33 and amplified as appropriate to the digitaltelevision receiver 31 via the HDMI(R) cable 35. The digital televisionreceiver 31 plays a content by displaying an image, and outputting audiobased on the pixel data and audio data supplied from the amplifier 32.

Also, the digital television receiver 31 and the amplifier 32 canexecute two-way communication such as IP communication or the like forexample, at high speed using the HDMI(R) cable 35, and the amplifier 32and the playback device 33 can also execute two-way communication suchas IP communication or the like for example, at high speed using theHDMI(R) cable 36.

That is to say, for example, the playback device 33 executes IPcommunication with the amplifier 32, whereby compressed pixel data andaudio data can be transmitted to the amplifier 32 via the HDMI(R) cable36 as data conforming to IP, and the amplifier 32 can receive thecompressed pixel data and audio data transmitted from the playbackdevice 33.

Also, the amplifier 32 executes IP communication with the digitaltelevision receiver 31, whereby compressed pixel data and audio data canbe transmitted to the digital television receiver 31 via the HDMI(R)cable 35 as data conforming to IP, and the digital television receiver31 can receive the compressed pixel data and audio data transmitted fromthe amplifier 32.

Accordingly, the digital television receiver 31 can transmit thereceived pixel data and audio data to the digital television receiver 34via the LAN cable 37. Also, the digital television receiver 31 decodesthe received pixel data and audio data, and based on uncompressed pixeldata and audio data obtained according to decoding, plays a content bydisplaying an image and outputting audio.

The digital television receiver 34 receives and decodes the pixel dataand audio data transmitted from the digital television receiver 31 viathe LAN cable 34, and based on uncompressed pixel data and audio dataobtained according to decoding, plays a content by displaying an imageand outputting audio. Thus, with the digital television receiver 31 andthe digital television receiver 34, the same or different content can beplayed simultaneously.

Further, in the case that the digital television receiver 31 hasreceived pixel data and audio data for playing a program which iscontent on air on television, when the received audio data is, forexample, 5.1-channel surround audio data or the like, and the digitaltelevision receiver 31 has difficulty in decoding the received audiodata, the digital television receiver 31 executes IP communication withthe amplifier 32, thereby transmitting the received audio data to theamplifier 32 via the HDMI(R) cable 35.

The amplifier 32 receives and decodes the audio data transmitted fromthe digital television receiver 31, and also amplifies the decoded audiodata as appropriate. Subsequently, 5.1-channel surround audio is playedwith a speaker (not shown) connected to the amplifier 32.

The digital television receiver 31 transmits audio data to the amplifier32 via the HDMI(R) cable 35, and also decodes the received pixel data,and based on the pixel data obtained by decoding, plays a program bydisplaying an image.

Thus, with the image transmission system in FIG. 2, electronic devicesconnected by the HDMI(R) cable 35 and HDMI(R) cable 36, such as thedigital television receiver 31, amplifier 32, playback device 33, andthe like can execute IP communication at high speed using the HDMI(R)cable, and accordingly, the LAN cable corresponding to the LAN cable 17in FIG. 1 does not have to be provided.

Also, the digital television receiver 31 and the digital televisionreceiver 34 are connected with the LAN cable 37, whereby the digitaltelevision receiver 31 can transmit the data received from the playbackdevice 33 via the HDMI(R) cable 36, amplifier 32, and HDMI(R) cable 35via the LAN cable 37, further to the digital television receiver 34, andaccordingly, the LAN cable and electronic device corresponding to theLAN cable 18 and hub 16 in FIG. 1 do not have to be provided.

Such as shown in FIG. 1, with an existing image transmission system,according to data to be transmitted/received and a communication method,the corresponding different cable has to be provided, and laying cablesfor connecting electronic devices is complicated. On the other hand,with the image transmission system shown in FIG. 2, two-waycommunication, such as IP communication or the like, can be executed athigh speed between electronic devices connected with an HDMI(R) cable,and accordingly, connection of the electronic devices can be simplified.That is to say, laying cables for connecting electronic devices, whichis conventionally complicated, can be further simplified.

Next, FIG. 3 illustrates a configuration example of an HDMI(R) sourceand an HDMI(R) sink built into each of the electronic devices connectedwith an HDMI(R) cable, e.g., the HDMI(R) sources provided within theamplifier 32 in FIG. 2, and the HDMI(R) sink provided within the digitaltelevision receiver 31.

The HDMI(R) source 71 and the HDMI(R) sink 72 are connected with asingle HDMI(R) cable 35, and the HDMI(R) source 71 and the HDMI(R) sink72 can execute two-way IP communication at high speed using the HDMI(R)cable 35 while maintaining the compatibility with the current HDMI(R).

The HDMI(R) source 71 transmits the differential signals correspondingto the pixel data of one screen worth of an uncompressed image to theHDMI(R) sink 72 in one direction using multiple channels during a validimage section (hereinafter also referred to as active video section asappropriate) that is a section obtained by removing a horizontal retracesection and a vertical retrace section from a section between onevertical synchronizing signal and the next vertical synchronizingsignal, and also transmits at least the differential signalscorresponding to audio data and control data accompanying the image,other auxiliary data, and the like to the HDMI(R) sink 72 in onedirection using multiple channels during a horizontal retrace section orvertical retrace section.

That is to say, the HDMI(R) source 71 includes a transmitter 81. Forexample, the transmitter 81 converts the pixel data of an uncompressedimage into the corresponding differential signals, and seriallytransmits these to the HDMI(R) sink 72 connected thereto via the HDMI(R)cable 35 using three TMDS channels #0, #1, and #2 which are multiplechannels in one direction.

Also, the transmitter 81 converts the audio data accompanying anuncompressed image, and further necessary control data, other auxiliarydata, and the like into the corresponding differential signals, andserially transmits these to the HDMI(R) sink 72 connected thereto viathe HDMI(R) cable 35 using the three TMDS channels #0, #1, and #2 in onedirection.

Further, the transmitter 81 transmits a pixel clock in sync with thepixel data transmitted through the three TMDS channels #0, #1, and #2 tothe HDMI(R) sink 72 connected thereto via the HDMI(R) cable 35 using theTMDS clock channel. Here, 10-bit pixel data is transmitted with a singleTMDS channel #i (i=0, 1, 2) during one clock of the pixel clock.

The HDMI(R) sink 72 receives the differential signals corresponding tothe pixel data, transmitted from the HDMI(R) source 71 in one directionusing the multiple channels during an active video section, and alsoreceives the differential signals corresponding to audio data andcontrol data, transmitted in one direction from the HDMI(R) source 71using the multiple channels during a horizontal retrace section orvertical retrace section.

That is to say, the HDMI(R) sink 72 includes a receiver 82. The receiver82 receives the differential signals corresponding to the pixel data,and the differential signals corresponding to the audio data and controldata, transmitted from the HDMI(R) source 71 connected thereto via theHDMI(R) cable 35 in one direction using the TMDS channels #0, #1, and #2in sync with the pixel clock transmitted through the TMDS clock channelsimilarly from the HDMI(R) source 71.

The transmission channels of the HDMI(R) system made up of the HDMI(R)source 71 and the HDMI(R) sink 72 include transmission channels calledas a DDC (Display Data Channel) 83 and a CEC line 84 in addition to thethree TMDS channels #0 through #2 serving as transmission channels fortransmitting pixel data and audio data from the HDMI(R) source 71 to theHDMI(R) sink 72 in one direction in sync with the pixel clock, and theTMDS clock channel serving as a transmission channel for transmittingthe pixel clock.

The DDC 83 is made up of two signal lines not shown included in theHDMI(R) cable 35, and is used for the HDMI(R) source 71 reading outE-EDID (Enhanced Extended Display Identification Data) from the HDMI(R)sink 72 connected thereto via the HDMI(R) cable 35.

That is to say, the HDMI(R) sink 72 includes EDIDROM (EDID ROM (ReadOnly Memory)) 85 which stores E-EDID that is information relating to thesettings and performance of the self device in addition to the receiver82. The HDMI(R) source 71 reads out the E-EDID stored in the EDIDROM 85of the HDMI(R) sink 72 via the DDC 83 from the HDMI(R) sink 72 connectedthereto via the HDMI(R) cable 35, and based on the E-EDID thereof,recognizes the settings and performance of the HDMI(R) sink 72, i.e.,for example, the image format (profile) corresponding to (an electronicdevice including) the HDMI(R) sink 72, e.g., RGB (Red, Green, Blue),YCbCr 4:4:4, YCbCr 4:2:2, or the like.

Note that, though not shown in the drawing, the HDMI(R) source 71 storesE-EDID, in the same way as the HDMI(R) sink 72, and can transmit theE-EDID thereof to the HDMI(R) sink 72 as appropriate.

The CEC line 84 is made up of a single signal line not shown included inthe HDMI(R) cable 35, and is used for executing two-way communication ofdata for control between the HDMI(R) source 71 and the HDMI(R) sink 72.

Also, the HDMI(R) source 71 and the HDMI(R) sink transmit a frameconforming to, for example, IEEE (Institute of Electrical andElectronics Engineers) 802.3 to the HDMI(R) sink 72 and the HDMI(R)source 71 via the DDC 83 or CEC line 84, whereby two-way IPcommunication can be executed.

Further, a signal line 86 connected to a pin called Hot Plug Detect isincluded in the HDMI(R) cable 35, and the HDMI(R) source 71 and theHDMI(R) sink 72 can detect connection of a new electronic device, i.e.,the HDMI(R) sink 72 or HDMI(R) source 71 using this signal line 86.

Next, FIG. 4 and FIG. 5 illustrate the pin-out (pin assignment) of aconnection not shown provided to the HDMI(R) source 71 or HDMI(R) sink72, connected to the HDMI(R) cable 35.

Note that, in FIG. 4 and FIG. 5, a pin number for determining a pin ofthe connector is described in the left column (the column of pins), andthe name of the signal assigned to the pin determined with a pin numberdescribed in the left column of the same row is described in the rightcolumn (the column of signal assignment).

FIG. 4 illustrates the pin-out of a connector called the Type-A ofHDMI(R).

Two signal lines which are differential signal lines where thedifferential signals TMDS Data#i+ and TMDS Data#i− of the TMDS channel#i are transmitted are connected to a pin to which the TMDS Data#i+ isassigned (the pins of which the pin numbers are 1, 4, and 7), and a pinto which the TMDS Data#i− is assigned (the pins of which the pin numbersare 3, 6, and 9).

Also, the CEC line 84 where the CEC signal which is data for control istransmitted is connected to a pin of which the pin number is 13, and apin of which the pin number is 14 is a reserved pin. If two-way IPcommunication can be executed using this reserved pin, the compatibilitywith the current HDMI(R) can be maintained. Therefore, in order totransmit a differential signal using the CEC line 84 and a signal lineconnected to the pin of which the pin number is 14 are subjected todifferential twist pair connection and shielded, and are grounded withthe ground lines of the CEC line 84 and DDC 83 connected to the pin ofwhich the pin number is 17.

Further, a signal line where a SDA (Serial Data) signal such as E-EDIDor the like is transmitted is connected to a pin of which the pin numberis 16, and a signal line where a SCL (Serial Clock) signal which is aclock signal used for synchronization at the time oftransmitting/receiving the SDA signal is transmitted is connected to apin of which the pin number is 15. The DDC in FIG. 3 is made up of asignal line where the SDA signal is transmitted, and a signal line wherethe SCL signal is transmitted.

Also, the signal line where the SDA signal is transmitted, and thesignal line where the SCL signal is transmitted are connected as adifferential twist pair and shielded so as to transmit a differentialsignal line, and is grounded with a ground line connected to a pin ofwhich the pin number is 17, in the same way as the CEC line 84 and thesignal line connected to the pin of which the pin number is 14.

Further, the signal line 86 where a signal for detecting connection of anew electronic device is transmitted is connected to a pin of which thepin number is 19.

FIG. 5 illustrates the pin-out of a connector called the Type-C orType-mini of HDMI(R).

Two signal lines which are differential signal lines where thedifferential signals TMDS Data#i+ and TMS Data#i− of the TMDS channel #iare transmitted are connected a pin to which the TMDS Data#i+ isassigned (pins of which the pin numbers are 2, 5, and 8), and a pin towhich the TMDS Data#i− is assigned (pins of which the pin numbers are 3,6, and 9).

Also, the CEC line 84 where the CEC signal is transmitted is connectedto a pin of which the pin number is 14, and a pin of which the pinnumber is 17is a reserved pin. A signal line connected to the pin ofwhich the pin number is 17, and the CEC line 84 are connected as adifferential twist pair and shielded in the same way as with the case ofType-A, and are grounded with the ground lines of the CEC line 84 andthe DDC 83 connected to a pin of which the pin number is 13.

Further, the signal line where the SDA signal is transmitted isconnected to the pin of which the pin number is 16, and the signal linewhere the SCL signal is transmitted is connected to the pin of which thepin number is 15. Also, the signal line where the SDA signal istransmitted, and the signal line where the SCL signal is transmitted areconnected as a differential twist pair and shielded so as to transmit adifferential signal, and is grounded with a ground line connected to apin of which the pin number is 13, in the same way as with the case ofType-A. Further, also, the signal line 86 where a signal for detectingconnection of a new electronic device is transmitted is connected to apin of which the pin number is 19.

Next, FIG. 6 is a diagram illustrating the configuration of the HDMI(R)source 71 and the HDMI(R) sink which execute IP communication by thehalf-duplex communication method using a signal line connected to areserved pin of the CEC line 84 and the connector of HDMI(R) connector.Note that FIG. 6 illustrates a configuration example of portionsrelating to half-duplex communication of the HDMI(R) source 71 andHDMI(R) sink 72. Also, in FIG. 6, the portions corresponding to those inthe case in FIG. 3 are denoted with the same reference numerals, anddescription thereof will be omitted as appropriate.

The HDMI(R) source 71 is configured of a transmitter 81, a switchingcontrol unit 121, and a timing control unit 122. Also, a conversion unit131, a decoding unit 132, and a switch 133 are provided to thetransmitter 81.

Tx data that is data to be transmitted from the HDMI(R) source 71 to theHDMI(R) sink 72 using two-way IP communication between the HDMI(R)source 71 and the HDMI(R) sink 72 is supplied to the conversion unit131. Examples of the Tx data include compressed pixel data and audiodata.

The conversion unit 131, which is configured of a differential amplifierfor example, converts the supplied Tx data into a differential signalmade up of two partial signals. Also, the conversion unit 131 transmitsthe differential signal obtained by conversion to the receiver 82 viathe CEC line 84, and a signal line 141 connected to a reserved pin ofthe connector not shown provided to the transmitter 81. That is to say,the conversion unit 131 supplies one of the partial signals making upthe differential signal obtained by conversion to the switch 133 via asignal line connected to the CEC line 84 of the HDMI(R) cable 35, whichis a signal line provided to the CEC line 84, more specifically to thetransmitter 81, and supplies the other partial signal making up thedifferential signal to the receiver 82 via a signal line connected tothe signal line 141 of the HDMI(R) cable 35, which is the signal line141, more specifically, the signal line provided to the transmitter 81,and the signal line 141.

The decoding unit 132 is configured of, for example, a differentialamplifier, and the input terminal thereof is connected to the CEC line84 and the signal line 141. The decoding unit 132 receives, based on thecontrol of the timing control unit 122, the differential signaltransmitted from the receiver 82 via the CEC line 84 and the signal line141, i.e., the differential signal made up of the partial signal on theCEC line 84, and the differential signal made up of the partial signalon the signal line 141, decodes this to Rx data that is the originaldata, and outputs this. The Rx data mentioned here is data to betransmitted from the HDMI(R) sink 72 to the HDMI(R) source 71 by two-wayIP communication between the HDMI(R) source 71 and the HDMI(R) sink 72,and examples thereof include a command for requesting transmission ofpixel data and audio data, or the like.

The CEC signal from the HDMI(R) source 71, or the partial signal makingup the differential signal corresponding to the Tx data from theconversion unit 131 is supplied to the switch 133 at timing fortransmitting data, and the CEC signal from the receiver 82, or thepartial signal making up the differential signal corresponding to the Rxdata from the receiver 82 is supplied to the switch 133 at timing forreceiving data. The switch 133 selects and outputs, based on the controlfrom the switching control unit 121, the CEC signal from the HDMI(R)source 71, or the CEC signal from the receiver 82, or the partial signalmaking up the differential signal corresponding to the Tx data, or thepartial signal making up the differential signal corresponding to the Rxdata.

That is to say, the switch 133 selects one of the CEC signal suppliedfrom the HDMI(R) source 71, and the partial signal supplied from theconversion unit 131 at timing for the HDMI(R) source 71 transmittingdata to the HDMI(R) sink 72, and transmits the selected CEC signal orpartial signal to the receiver 82 via the CEC line 84.

Also, the switch 133 receives the CEC signal transmitted from thereceiver 82 via the CEC line 84, or the partial signal of thedifferential signal corresponding to the Rx data at timing for theHDMI(R) source 71 receiving the data transmitted from the HDMI(R) sink72, and supplies the received CEC signal or partial signal to theHDMI(R) source 71 or decoding unit 132.

The switching control unit 121 controls the switch 133 to switch theswitch 133 so as to select one of the signals supplied to the switch133. The timing control unit 122 controls the reception timing of thedifferential signal by the decoding unit 132.

Also, the HDMI(R) sink 72 is configured of the receiver 82, timingcontrol unit 123, and switching control unit 124. Further, a conversionunit 134, a switch 135, and a decoding unit 136 are provided to thereceiver 82.

The conversion unit 134 is configured of, for example, a differentialamplifier, and the Rx data is supplied to the conversion unit 134. Theconversion unit 134 converts, based on the control of the timing controlunit 123, the supplied Rx data into a differential signal made up of twopartial signals, and transmits the differential signal obtained byconversion to the transmitter 81 via the CEC line 84 and the signal line141. That is to say, the conversion unit 134 supplies one of the partialsignals making up the differential signal obtained by conversion to theswitch 135 via a signal line connected to the CEC line 84 of the HDMI(R)cable 35, which is a signal line provided to the CEC line 84, morespecifically to the receiver 82, and supplies the other partial signalmaking up the differential signal to the transmitter 81 via a signalline connected to the signal line 141 of the HDMI(R) cable 35, which isthe signal line 141, more specifically, the signal line provided to thereceiver 82, and the signal line 141.

The CEC signal from the transmitter 81, or the partial signal making upthe differential signal corresponding to the Tx data from thetransmitter 81 is supplied to the switch 135 at timing for receivingdata, and the partial signal making up the differential signalcorresponding to the Rx data from the conversion unit 134, or the CECsignal from the HDMI(R) sink 72 is supplied to the switch 135 at timingfor transmitting data. The switch 135 selects and outputs, based on thecontrol from the switching control unit 124, the CEC signal from thetransmitter 81, or the CEC signal from the HDMI(R) sink 72, or thepartial signal making up the differential signal corresponding to the Txdata, or the partial signal making up the differential signalcorresponding to the Rx data.

That is to say, the switch 135 selects one of the CEC signal suppliedfrom the HDMI(R) sink 72, and the partial signal supplied from theconversion unit 134 at timing for the HDMI(R) sink 72 transmitting datato the HDMI(R) source 71, and transmits the selected CEC signal orpartial signal to the transmitter 81 via the CEC line 84.

Also, the switch 135 receives the CEC signal transmitted from thetransmitter 81 via the CEC line 84, or the partial signal of thedifferential signal corresponding to the Tx data at timing for theHDMI(R) sink 72 receiving the data transmitted from the HDMI(R) source71, and supplies the received CEC signal or partial signal to theHDMI(R) sink 72 or decoding unit 136.

The decoding unit 136 is configured of, for example, a differentialamplifier, and the input terminal thereof is connected to the CEC line84 and the signal line 141. The decoding unit 136 receives thedifferential signal transmitted from the transmitter 81 via the CEC line84 and the signal line 141, i.e., the differential signal made up of thepartial signal on the CEC line 84, and the partial signal on the signalline 141, decodes this to Tx data that is the original data, and outputsthis.

The switching control unit 124 controls the switch 135 to switch theswitch 135 so as to select one of the signals supplied to the switch135. The timing control unit 123 controls the transmission timing of thedifferential signal by the conversion unit 134.

Also, in the case that the HDMI(R) source 71 and the HDMI(R) sink 72execute IP communication by the full-duplex communication method usingthe signal line 141 connected to the CEC line 84 and the reserved pin,and a signal line where the SDA signal is transmitted, and a signal linewhere the SCL signal is transmitted, the HDMI(R) source 71 and theHDMI(R) sink 72 are configured such as shown in FIG. 7, for example.Note that, in FIG. 7, the portions corresponding to those in the case inFIG. 6 are denoted with the same reference numerals, and descriptionthereof will be omitted as appropriate.

The HDMI(R) source 71 is configured of a transmitter 81, a switchingcontrol unit 121, and a switching control unit 171. Also, a conversionunit 131, a switch 133, a switch 181, a switch 182, and a decoding unit183 are provided to the transmitter 81.

The SDA signal from the HDMI(R) source 71 is supplied to the switch 181at timing for transmitting data, and the SDA signal from the receiver82, or the partial signal making up the differential signalcorresponding to the Rx data from the receiver 82 is supplied to theswitch 181 at timing for receiving data. The switch 181 selects andoutputs, based on the control from the switching control unit 171, theSDA signal from the HDMI(R) source 71, or the SDA signal from thereceiver 82, or the partial signal making up the differential signalcorresponding to the Rx data.

That is to say, the switch 181 receives the SDA signal transmitted fromthe receiver 82 via the SDA line 191 which is a signal line over whichSDA signals are transmitted, or the partial signal of the differentialsignal corresponding to the Rx data at timing for the HDMI(R) source 71receiving the data transmitted from the HDMI(R) sink 72, and suppliesthe received SDA signal or partial signal to the HDMI(R) source 71 ordecoding unit 183.

Also, the switch 181 transmits the SDA signal supplied from the HDMI(R)source 71 to the receiver 82 via the SDA line 191 or transmits nothingto the receiver 82 at timing for the HDMI(R) source 71 transmitting datato the HDMI(R) sink 72.

The SCL signal from the HDMI(R) source 71 is supplied to the switch 182at timing for transmitting data, and the partial signal making up thedifferential signal corresponding to the Rx data from the receiver 82 issupplied to the switch 182 at timing for receiving data. The switch 182selects and outputs, based on the control from the switching controlunit 171, one of the SCL signal, and the partial signal making up thedifferential signal corresponding to the Rx data.

That is to say, the switch 182 receives the partial signal of thedifferential signal corresponding to the Rx data, transmitted from thereceiver 82 via the SCL line 192 that is a signal line where the SCLsignal is transmitted, at timing for the HDMI(R) source 71 receiving thedata transmitted from the HDMI(R) sink 72 to supply the received partialsignal to the decoding unit 183, or receives nothing.

Also, the switch 182 transmits the SCL signal supplied from the HDMI(R)source 71 to the receiver 82 via the SCL line 192, or transmits nothingto the receiver 82 at timing for the HDMI(R) source 71 transmitting datato the HDMI(R) sink 72.

The decoding unit 183 is configured of, for example, a differentialamplifier, and the input terminal thereof is connected to the SDA line191 and the SCL line 192. The decoding unit 183 receives thedifferential signal transmitted from the receiver 82 via the SDA line191 and the SCL line 192, i.e., the differential signal made up of thepartial signal on the SDA line 191, and the partial signal on the SCLline 192, decodes this to Rx data that is the original data, and outputsthis.

The switching control unit 171 controls the switch 181 and the switch182 to switch the switch 181 and the switch 182 so as to select one ofthe signals supplied to the switch 181 and the switch 182.

Also, the HDMI(R) sink 72 is configured of the receiver 82, switchingcontrol unit 124, and switching control unit 172. Further, the switch135, the decoding unit 136, a conversion unit 184, a switch 185, and aswitch 186 are provided to the receiver 82.

The conversion unit 184 is configured of, for example, a differentialamplifier, and the Rx data is supplied to the conversion unit 184. Theconversion unit 184 converts the supplied Rx data into a differentialsignal made up of two partial signals, and transmits the differentialsignal obtained by conversion to the transmitter 81 via the SDA line 191and the SCL line 192. That is to say, the conversion unit 184 transmitsone of the partial signals making up the differential signal obtained byconversion to the transmitter 81 via the switch 185, and transmits theother partial signal making up the differential signal to thetransmitter 81 via the switch 186.

The partial signal making up the differential signal corresponding tothe Rx data from the conversion unit 184, and the SDA signal from theHDMI(R) sink 72 are supplied to the switch 185 at timing fortransmitting data, and the SDA signal from the transmitter 81 issupplied to the switch 185 at timing for receiving data. The switch 185selects and outputs, based on the control from the switching controlunit 172, the SDA signal from the HDMI(R) sink 72, or the SDA signalfrom the transmitter 81, or the partial signal making up thedifferential signal corresponding to the Rx data.

That is to say, the switch 185 receives the SDA signal transmitted fromthe transmitter 81 via the SDA line 191 at timing for the HDMI(R) sink72 receiving the data transmitted from the HDMI(R) source 71 to supplythe received SDA signal to the HDMI(R) sink 72, or receives nothing.

Also, the switch 185 transmits the SDA signal supplied from the HDMI(R)sink 72, or the partial signal supplied from the conversion unit 184 tothe transmitter 81 via the SDA line 191 at timing for the HDMI(R) sink72 transmitting data to the HDMI(R) source 71.

The partial signal making up the differential signal corresponding tothe Rx data from the conversion unit 184 is supplied to the switch 186at timing for transmitting data, and the SCL signal from the transmitter81 is supplied to the switch 186 at timing for receiving data. Theswitch 186 selects and outputs, based on the control from the switchingcontrol unit 172, one of the partial signal making up the differentialsignal corresponding to the Rx data, and the SCL signal.

That is to say, the switch 186 receives the SCL signal transmitted fromthe transmitter 81 via the SCL line 192 at timing for the HDMI(R) sink72 receiving the data transmitted from the HDMI(R) source 71 to supplythe received SCL signal to the HDMI(R) sink 72, or receives nothing.

Also, the switch 186 transmits the partial signal supplied from theconversion unit 184 to the transmitter 81 via the SCL line 192, ortransmits nothing to the transmitter 81 at timing for the HDMI(R) sink72 transmitting data to the HDMI(R) source 71.

The switching control unit 172 controls the switch 185 and the switch186 to switch the switch 185 and the switch 186 so as to select one ofthe signals supplied to the switch 185 and the switch 186.

Incidentally, in the case that the HDMI(R) source 71 and the HDMI(R)sink 72 execute IP communication, it is determined depending on theconfiguration of each of the HDMI(R) source 71 and the HDMI(R) sink 72whether half-duplex communication is available, or full-duplexcommunication is available. Therefore, the HDMI(R) source 71 determineswhether to execute half-duplex communication, full-duplex communication,or two-way communication by exchanging the CEC signal with reference tothe E-EDID received from the HDMI(R) sink 72.

The E-EDID that the HDMI(R) source 71 receives is made up of, forexample such as shown in FIG. 8, a basic block and an extended block.

Data determined with the E-EDID 1.3 standard represented by “E-EDID 1.3Basic Structure” is disposed at the head of the basic block of theE-EDID, and subsequently, timing information for maintainingcompatibility with the conventional EDID represented by “Preferredtiming”, and timing information represented by “2nd timing” differentfrom “Preferred timing” for maintaining compatibility with theconventional EDID are disposed.

Also, with the basic block, information indicating the name of a displaydevice represented by “Monitor NAME”, and information indicating thenumber of displayable pixels regarding a case where the aspect ratio is4:3 and 16:9 represented by “Monitor Range Limits” are disposed in orderfollowing the “2nd timing”.

On the other hand, information relating to left and right speakersrepresented by “Speaker Allocation” is disposed at the head of theextended block, and subsequently, data represented by “VIDEO SHORT” inwhich the displayable image size, frame rate, and information indicatingwhether to be interlace or progressive, and information of the aspectratio and the like are described, data represented by “AUDIO SHORT” inwhich information such as a playable audio codec method, a samplingfrequency, a cut-off band, a codec bit count, and the like aredescribed, and information relating to left and right speakersrepresented by “Speaker Allocation” are disposed in order.

Also, with the extended block, data defined uniquely for each makerrepresented by “Vender Specific”, timing information for maintainingcompatibility with the conventional EDID represented by “3rd timing”,and timing information for maintaining compatibility with theconventional EDID represented by “4th timing” are disposed following“Speaker Allocation”.

Further, the data represented by “Vender Specific” is made up of a datastructure shown in FIG. 9. That is to say, the 0th block through the Nthblock that are 1-byte blocks are provided to the data represented by“Vender Specific”.

With the 0th block disposed at the head of the data represented by“Vender Specific”, a header indicating the data region of the data“Vender Specific” represented by “Vender-Specific tag code(=3)”, andinformation indicating the length of the data “Vender Specific”represented by “Length(=N)” are disposed.

Also, with the 1st block through the 3rd block, information indicating anumber “0x000003” registered for HDMI(R) represented by “24 bit IEEERegistration Identifier(0x000C03)LSB first” is disposed. Further, withthe 4th block and the 5th block, information indicating the physicaladdress of a 24-bit sink device represented with each of “A”, “B”, “C”,and “D” is disposed.

With the 6th block, a flag indicating a function that the sink devicecan handle represented by “Supports-AI”, information for specifying thenumber of bits per one pixel represented with each of “DC-48 bit”,“DC-36 bit”, and “DC-30 bit”, a flag indicating whether or not the sinkdevice can handle transmission of image of YCbCr4:4:4 represented by“DC-Y444”, and a flag indicating whether or not the sink device canhandle a dual DVI (Digital Visual Interface) represented by “DVI-Dual”are disposed.

Also, with the 7th block, information indicating the maximum frequencyof the TMDS pixel clock represented by “Max-TMDS-Clock” is disposed.Further, with the 8th block, a flag indicating whether or not there isthe delay information of video and audio represented by “Latency”, afull-duplex flag indicating whether or not full-duplex communication isavailable represented by “Full Duplex”, and a half-duplex flagindicating whether or not half-duplex communication is availablerepresented by “Half Duplex” are disposed.

Here, the full-duplex flag that has been set (e.g., set to “1”)indicates that the HDMI(R) sink 72 has a function for executingfull-duplex communication, i.e., has a configuration shown in FIG. 7,and the full-duplex flag that has been reset (e.g., set to “0”)indicates that the HDMI(R) sink 72 has no function for executingfull-duplex communication.

Similarly, the half-duplex flag that has been set (e.g., set to “1”)indicates that the HDMI(R) sink 72 has a function for executinghalf-duplex communication, i.e., has a configuration shown in FIG. 6,and the half-duplex flag that has been reset (e.g., set to “0”)indicates that the HDMI(R) sink 72 has no function for executinghalf-duplex communication.

Also, With the 9th block of data represented by “Vender Specific”, thedelay time data of progressive video represented by “Video Latency” isdisposed, and with the 10th block, the delay time data of audioaccompanying progressive video represented by “Audio Latency” isdisposed. Further, with the 11th block, the delay time data of interlacevideo represented by “Interlaced Video Latency” is disposed, and withthe 12th block, the delay time data of audio accompanying interlacevideo represented by “Interlaced Audio Latency” is disposed.

The HDMI(R) source 71 determines whether half-duplex communication isexecuted, full-duplex communication is executed, or two-waycommunication according to exchange of the CEC signal is executed, basedon the full-duplex flag and the half-duplex flag included in the E-EDIDreceived from the HDMI(R) sink 72, and executes two-way communicationwith the HDMI(R) sink 72 in accordance with the determination resultthereof.

For example, in the case that the HDMI(R) source 71 is configured suchas shown in FIG. 6, the HDMI(R) source can execute half-duplexcommunication with the HDMI(R) sink 72 shown in FIG. 6, but hasdifficulty in executing half-duplex communication with the HDMI(R) sink72, shown in FIG. 7.

Therefore, upon the power supply of the electronic device provided tothe HDMI(R) source 71 being turned on, the HDMI(R) source 71 startscommunication processing, and executes two-way communication accordingto the function included in the HDMI(R) sink 72 connected to the HDMI(R)source 71.

Description will be made below regarding the communication processing bythe HDMI(R) source 71 shown in FIG. 6 with reference to the flowchart inFIG. 10.

In step S11, the HDMI(R) source 71 determines whether or not a newelectronic device has been connected to the HDMI(R) source 71. Forexample, the HDMI(R) source 71 determines whether or not a newelectronic device to which the HDMI(R) sink 72 is provided has beenconnected, based on the magnitude of the voltage applied to a pin calledHot Plug Detect to which the signal line 86 is connected.

In the case that determination is made in step S11 that a new electronicdevice has not been connected, communication is not executed, andaccordingly, the communication processing ends.

On the other hand, in the case that determination is made in step S11that a new electronic device has been connected, in step S12 theswitching control unit 121 controls the switch 133 to switch the switch133 so as to select the CEC signal from the HDMI(R) source 71 at thetime of transmitting data, and to select the CEC signal from thereceiver 82 at the time of receiving data.

In step S13, the HDMI(R) source 71 receives the E-EDID transmitted fromthe HDMI(R) sink 72 via the DDC 83. That is to say, upon detectingconnection of the HDMIR(R) source 71, the HDMI(R) sink 72 reads out theE-EDID from the EDIDROM 85, and transmits the readout E-EDID to theHDMI(R) source 71 via the DDC 83, and accordingly, the HDMI(R) source 71receives the E-EDID transmitted from the HDMI(R) sink 72.

In step S14, the HDMI(R) source 71 determines whether or not half-duplexcommunication with the HDMI(R) sink 72 is available. That is to say, theHDMI(R) source 71 determines whether or not the half-duplex flag “HalfDuplex” in FIG. 9 has been set, with reference to the E-EDID receivedfrom the HDMI(R) sink 72, and for example, in the case that thehalf-duplex flag has been set, the HDMI(R) source 71 determines thattwo-way IP communication by the half-duplex communication method, i.e.,half-duplex communication is available.

In the case that determination is made in step S14 that half-duplexcommunication is available, in step S15 the HDMI(R) source 71 transmitsa signal to the effect that IP communication will be performed with thehalf-duplex communication method using the CEC line 84 and the signalline 141, to the receiver 82 via the switch 133 and the CEC line 84, aschannel information indicating the channel to be used for bidirectionalcommunication.

That is to say, in the case that the half-duplex flag has been set, theHDMI(R) source 71 can recognize that the HDMI(R) sink 72 is configuredsuch as shown in FIG. 6, and half-duplex communication using the CECline 84 and the signal line 141 is available, and accordingly, transmitsthe channel information to the HDMI(R) sink 72 to notify thathalf-duplex communication is executed.

In step S16, the switching control unit 121 controls the switch 133 toswitch the switch 133 so as to select the differential signalcorresponding to the Tx data from the conversion unit 131 at the time oftransmitting data, and so as to select the differential signalcorresponding to the Rx data from the receiver 82 at the time ofreceiving data.

In step S17, each unit of the HDMI(R) source 71 executes two-way IPcommunication with the HDMI(R) sink 72 by the half-duplex communicationmethod, and the communication processing ends. Specifically, theconversion unit 131 converts the Tx data supplied from the HDMI(R)source 71 into a differential signal at the time of transmitting data,supplies one of the partial signals making up the differential signalobtained by conversion to the switch 133, and transmits the otherpartial signal to the receiver 82 via the signal line 141. The switch133 transmits the partial signal supplied from the conversion unit 131to the receiver 82 via the CEC line 84. Thus, the differential signalcorresponding to the Tx data is transmitted from the HDMI(R) source 71to the HDMI(R) sink 72.

Also, the decoding unit 132 receives the differential signalcorresponding to the Rx data transmitted from the receiver 82 at thetime of receiving data. That is to say, the switch 133 receives thepartial signal of the differential signal corresponding to the Rx data,transmitted from the receiver 82 via the CEC line 84, and supplies thereceived partial signal to the decoding unit 132. Under control of thetiming control unit 122, the decoding unit 132 decodes the differentialsignal made up of the partial signal supplied from the switch 133, andthe partial signal supplied from the receiver 82 via the signal line 141to Rx data that is the original data, and outputs this to the HDMI(R)source 71.

Thus, the HDMI(R) source 71 executes exchange of various types of datawith the HDMI(R) sink 72, such as control data, pixel data, audio data,and the like.

Also, in the case that determination is made in step S14 thathalf-duplex communication is not available, in step S18 each unit of theHDMI(R) source 71 executes transmission/reception of the CEC signal,thereby executing two-way communication with the HDMI(R) sink 72, andthe communication processing ends.

That is to say, the HDMI(R) source 71 transmits the CEC signal to thereceiver 82 via the switch 133 and the CEC line 84 at the time oftransmitting data, and the HDMI(R) source 71 receives the CEC signaltransmitted from the receiver 82 via the switch 133 and the CEC line 84at the time of receiving data, thereby executing exchange of controldata with the HDMI(R) sink 72.

Thus, the HDMI(R) source 71 references the half-duplex flag to executehalf-duplex communication with the HDMI(R) sink 72 capable ofhalf-duplex communication using the CEC line 84 and the signal line 141.

Thus, the HDMI(R) source 71 switches the switch 133 to select data to betransmitted and data to be received, and executes half-duplexcommunication using the CEC line 84 and the signal line 141, i.e., IPcommunication by the half-duplex communication method with the HDMI(R)sink 72, whereby high-speed two-way communication can be executed whilemaintaining compatibility with the conventional HDMI(R).

Also, similar to the HDMI(R) source 71, upon the power supply of theelectronic device provided to the HDMI(R) sink 72 being turned on, theHDMI(R) sink 72 also starts communication processing, and executestwo-way communication with the HDMI(R) source 71.

Description will be made below regarding the communication processing bythe HDMI(R) sink 72 shown in FIG. 6 with reference to the flowchart inFIG. 11.

In step S41, the HDMI(R) sink 72 determines whether or not a newelectronic device has been connected to the HDMI(R) sink 72. Forexample, the HDMI(R) sink 72 determines whether or not a new electronicdevice to which the HDMI(R) source 71 is provided has been connected,based on the magnitude of the voltage applied to a pin called Hot PlugDetect to which the signal line 86 is connected.

In the case that determination is made in step S41 that a new electronicdevice has not been connected, communication is not executed, andaccordingly, the communication processing ends.

On the other hand, in the case that determination is made in step S41that a new electronic device has been connected, in step S42 theswitching control unit 124 controls the switch 135 to switch the switch135 so as to select the CEC signal from the HDMI(R) sink 72 at the timeof transmitting data, and so as to select the CEC signal from thetransmitter 81 at the time of receiving data.

In step S43, the HDMI(R) sink 72 reads out E-EDID from the EDIDROM 85,and transmits the readout E-EDID to the HDMI(R) source 71 via the DDC83.

In step S44, the HDMI(R) sink 72 determines whether or not the channelinformation transmitted from the HDMI(R) source 71 has been received.

That is to say, the channel information indicating the channel oftwo-way communication is transmitted according to the functions that theHDMI(R) source 71 and the HDMI(R) sink 72 have. For example, in the casethat the HDMI(R) source 71 is configured such as shown in FIG. 6, theHDMI(R) source 71 and the HDMI(R) sink 72 can execute half-duplexcommunication using the CEC line 84 and the signal line 141, andaccordingly, channel information to the effect that IP communication isexecuted using the CEC line 84 and the signal line 141 is transmittedfrom the HDMI(R) source 71 to the HDMI(R) sink 72. The HDMI(R) sink 72receives the channel information transmitted from the HDMI(R) source 71via the switch 135 and the CEC line 84, and determines that the channelinformation has been received.

On the other hand, in the case that the HDMI(R) source 71 does not havea function for executing half-duplex communication, the channelinformation has not been transmitted from the HDMI(R) source 71 to theHDMI(R) sink 72, and accordingly, the HDMI(R) sink 72 determines that nochannel information has been received.

In the case that determination is made in step S44 that the channelinformation has been received, the processing proceeds to step S45,where the switching control unit 124 controls the switch 135 to switchthe switch 135 so as to select the differential signal corresponding tothe Rx data from the conversion unit 134 at the time of transmittingdata, and so as to select the differential signal corresponding to theTx data from the transmitter 81 at the time of receiving data.

In step S46, each unit of the HDMI(R) sink 72 executes two-way IPcommunication with the HDMI(R) source 71 by the half-duplexcommunication method, and the communication processing ends.Specifically, the conversion unit 134 converts the Rx data supplied fromthe HDMI(R) sink 72 into a differential signal based on the control ofthe timing control unit 123 at the time of transmitting data, andsupplies one of the partial signals making up the differential signalobtained by conversion to the switch 135, and transmits the otherpartial signal to the transmitter 81 via the signal line 141. The switch135 transmits the partial signal supplied from the conversion unit 134to the transmitter 81 via the CEC line 84. Thus, the differential signalcorresponding to the Rx data is transmitted from the HDMI(R) sink 72 tothe HDMI(R) source 71.

Also, the decoding unit 136 receives the differential signalcorresponding to the Tx data transmitted from the transmitter 81 at thetime of receiving data. That is to say, the switch 135 receives thepartial signal of the differential signal corresponding to the Tx data,transmitted from the transmitter 81 via the CEC line 84, and suppliesthe received partial signal to the decoding unit 136. The decoding unit136 decodes the differential signal made up of the partial signalsupplied from the switch 135, and the partial signal supplied from thetransmitter 81 via the signal line 141 to Tx data that is the originaldata, and outputs this to the HDMI(R) sink 72.

Thus, the HDMI(R) sink 72 executes exchange of various types of datawith the HDMI(R) source 71, such as control data, pixel data, audiodata, and the like.

Also, in the case that determination is made in step S44 that thechannel information has not been received, in step S47 each unit of theHDMI(R) sink 72 executes transmission/reception of the CEC signal,thereby executing two-way communication with the HDMI(R) source 71, andthe processing ends.

That is to say, the HDMI(R) sink 72 transmits the CEC signal to thetransmitter 81 via the switch 135 and the CEC line 84 at the time oftransmitting data, and the HDMI(R) sink 72 receives the CEC signaltransmitted from the transmitter 81 via the switch 135 and the CEC line84 at the time of receiving data, thereby executing exchange of controldata with the HDMI(R) source 71.

Thus, upon receiving the channel information, the HDMI(R) sink 72executes half-duplex communication with the HDMI(R) sink 72 using theCEC line 84 and the signal line 141.

Thus, the HDMI(R) sink 72 switches the switch 135 to select data to betransmitted and data to be received, and executes half-duplexcommunication with the HDMI(R) source 71 using the CEC line 84 and thesignal line 141, whereby high-speed two-way communication whilemaintaining compatibility with the conventional HDMI(R).

Also, in the case that the HDMI(R) source 71 is configured such as shownin FIG. 7, with the communication processing, the HDMI(R) source 71determines whether or not the HDMI(R) sink 72 has a function forexecuting full-duplex communication, based on the full-duplex flagincluded in the E-EDID, and executes two-way communication according tothe determination result thereof.

Description will be made below regarding the communication processing bythe HDMI(R) source 71 shown in FIG. 7 with reference to the flowchart inFIG. 12.

In step S71, the HDMI(R) source 71 determines whether or not a newelectronic device has been connected to the HDMI(R) source 71. In thecase that determination is made in step S71 that a new electronic devicehas not been connected, communication is not executed, and accordingly,the communication processing ends.

On the other hand, in the case that determination is made in step S71that a new electronic device has been connected, in step S72 theswitching control unit 171 controls the switch 181 and the switch 182 toswitch the switch 181 and the switch 182 so as to select the SDA signalfrom the HDMI(R) source 71 by the switch 181 and select the SCL signalfrom the HDMI(R) source 71 by the switch 182 at the time of transmittingdata, and so as to select the SDA signal from the receiver 82 by theswitch 181 at the time of receiving data.

In step S73, the switching control unit 121 controls the switch 133 toswitch the switch 133 so as to select the CEC signal from the HDMI(R)source 71 at the time of transmitting data, and so as to select the CECsignal from the receiver 82 at the time of receiving data.

In step S74, the HDMI(R) source 71 receives the E-EDID transmitted fromthe HDMI(R) sink 72 via the SDA line 191 of the DDC 83. That is to say,upon detecting connection of the HDMI(R) source 71, the HDMI(R) sink 72reads out E-EDID from the EDIDROM 85, and transmits the readout streamto the HDMI(R) source 71 via the SDA line 191 of the DDC 83, andaccordingly, the HDMI(R) source 71 receives the E-EDID transmitted fromthe HDMI(R) sink 72.

In step S75, the HDMI(R) source 71 determines whether or not full-duplexcommunication with the HDMI(R) sink 72 is available. That is to say, theHDMI(R) source 71 references the E-EDID received from the HDMI(R) sink72 to determine whether or not the full-duplex flag “Full Duplex” inFIG. 9 has been set, and for example, in the case that the full-duplexflag has been set, the HDMI(R) source 71 determines that two-way IPcommunication by the full-duplex communication method, i.e., full-duplexcommunication is available.

In the case that determination is made in step S75 that full-duplexcommunication is available, in step S76 the switching control unit 171controls the switch 181 and the switch 182 to switch the switch 181 andthe switch 182 to select the differential signal corresponding to the Rxdata from the receiver 82 at the time of receiving data.

That is to say, the switching control unit 171 switches the switch 181and the switch 182 so as to select the partial signal transmitted viathe SDA line 191 using the switch 181, and so as to select the partialsignal transmitted via the SCL line 192 using the switch 182, of thepartial signals making up the differential signal corresponding to theRx data, transmitted from the receiver 82 at the time of receiving data.

The SDA line 191 and the SCL line 192 making up the DDC 83 are not usedafter the E-EDID is transmitted from the HDMI(R) sink 72 to the HDMI(R)source 71, i.e., transmission/reception of the SDA signal and the SCLsignal via the SDA line 191 and the SCL line 192 is not executed, andaccordingly, the SDA line 191 and the SCL line 192 can be used as thetransmission paths of the Rx data according to full-duplex communicationby switching the switch 181 and the switch 182.

In step S77, the HDMI(R) source 71 transmits a signal to the effect thatIP communication by the full-duplex communication method using the CECline 84 and the signal line 141, and the SDA line 191 and the SCL line192 as the channel information indicating a two-way communicationchannel, to the receiver 82 via the switch 133 and the CEC line 84.

That is to say, in the case that the full-duplex flag has been set, theHDMI(R) source 71 can recognize that the HDMI(R) sink 72 is configuredsuch as shown in FIG. 7, and full-duplex communication using the CECline 84 and the signal line 141, and the SDA line 191 and the SCL line192 is available, and accordingly, transmits the channel information tothe HDMI(R) sink 72 to notify that full-duplex communication isexecuted.

In step S78, the switching control unit 121 controls the switch 133 toswitch the switch 133 so as to select the differential signalcorresponding to the Tx data from the conversion unit 131 at the time oftransmitting data. That is to say, the switching control unit 121switches the switch 133 so as to select the partial signal of thedifferential signal corresponding to the Tx data supplied from theconversion unit 131 to the switch 133.

In step S79, each unit of the HDMI(R) source 71 executes two-way IPcommunication with the HDMI(R) sink 72 by the full-duplex communicationmethod, and the communication processing ends. Specifically, theconversion unit 131 converts the Tx data supplied from the HDMI(R)source 71 into a differential signal, supplies one of the partialsignals making up the differential signal obtained by conversion to theswitch 133, and transmits the other partial signal to the receiver 82via the signal line 141, at the time of transmitting data. The switch133 transmits the partial signal supplied from the conversion unit 131to the receiver 82 via the CEC line 84. Thus, the differential signalcorresponding to the Tx data is transmitted from the HDMI(R) source 71to the HDMI(R) sink 72.

Also, the decoding unit 183 receives the differential signalcorresponding to the Rx data transmitted from the receiver 82 at thetime of receiving data. That is to say, the switch 181 receives thepartial signal of the differential signal corresponding to the Rx data,transmitted from the receiver 82 via the SDA line 191, and supplies thereceived partial signal to the decoding unit 183. Also, the switch 182receives the other partial signal of the differential signalcorresponding to the Rx data, transmitted form the receiver 82 via theSCL line 192, and supplies the received partial signal to the decodingunit 183. The decoding unit 183 decodes the differential signal made upof the partial signal supplied from the switch 181 and the switch 182 toRx data that is the original data, and outputs this to the HDMI(R)source 71.

Thus, the HDMI(R) source 71 executes exchange of various types of datawith the HDMI(R) sink 72, such as control data, pixel data, audio data,and the like.

Also, in the case that determination is made in step S75 thatfull-duplex communication is not available, in step S80 each unit of theHDMI(R) source 71 executes transmission/reception of the CEC signal,thereby executing two-way communication with the HDMI(R) sink 72, andthe communication processing ends.

That is to say, the HDMI(R) source 71 transmits the CEC signal to thereceiver 82 via the switch 133 and the CEC line 84 at the time oftransmitting data, and the HDMI(R) source 71 receives the CEC signaltransmitted from the receiver 82 via the switch 133 and the CEC lien 84at the time of receiving data, thereby executing exchange of controldata with the HDMI(R) sink 72.

Thus, the HDMI(R) source 71 references the full-duplex flag to executefull-duplex communication with the HDMI(R) sink 72 capable offull-duplex communication using the CEC line 84 and the signal line 141,and the SDA line 191 and the SCL line 192.

Thus, full-duplex communication is executed with the HDMI(R) sink 72using the CEC line 84 and the signal line 141, and the SDA line 191 andthe SCL line 192 by switching the switch 133, the switch 181, and theswitch 182, to select data to be transmitted and data to be received,whereby high-speed two-way communication can be executed whilemaintaining compatibility with the conventional HDMI(R).

Also, even in the case that the HDMI(R) sink 72 is configured such asshown in FIG. 7, the HDMI(R) sink 72 executes the communicationprocessing in the same way as with the case of the HDMI(R) sink 72 shownin FIG. 6, thereby executing two-way communication with the HDMI(R)source 71.

Description will be made below regarding the communication processing bythe HDMI(R) sink 72 shown in FIG. 7 with reference to the flowchart inFIG. 13.

In step S111, the HDMI(R) sink 72 determines whether or not a newelectronic device has been connected to the HDMI(R) sink 72. In the casethat determination is made in step S111 that a new electronic device hasnot been connected, communication is not executed, and accordingly, thecommunication processing ends.

On the other hand, in the case that determination is made in step S111that a new electronic device has been connected, in step S112 theswitching control unit 172 controls the switch 185 and the switch 186 toswitch the switch 185 and the switch 186 so as to select the SDA signalfrom the HDMI(R) sink 72 by the switch 185 at the time of transmittingdata, and further so as to select the SDA signal from the transmitter 81by the switch 185 at the time of receiving data, and select the SCLsignal from the transmitter 81 by the switch 186.

In step S113, the switching control unit 124 controls the switch 135 toswitch the switch 135 so as to select the CEC signal from the HDMI(R)sink 72 at the time of transmitting data, and so as to select the CECsignal from the transmitter 81 at the time of receiving data.

In step S114, the HDMI(R) sink 72 reads out E-EDID from the EDIDROM 85,and transmits the readout E-EDID to the HDMI(R) source 71 via the switch185 and the SDA line 191 of the DDC 83.

In step S115, the HDMI(R) sink 72 determines whether or not the channelinformation transmitted from the HDMI(R) source 71 has been received.

That is to say, the channel information indicating the two-waycommunication channel is transmitted from the HDMI(R) source 71according to the functions that the HDMI(R) source 71 and the HDMI(R)sink 72 have. For example, in the case that the HDMI(R) source 71 isconfigured such as shown in FIG. 7, the HDMI(R) source 71 and theHDMI(R) sink 72 can execute full-duplex communication, and accordingly,channel information to the effect that IP communication by thefull-duplex communication method using the CEC line 84 and the signalline 141, and the SDA line 191 and the SCL line 192 is executed, istransmitted from the HDMI(R) source 71 to the HDMI(R) sink 72, andaccordingly, the HDMI(R) sink 72 receives the channel informationtransmitted from the HDMI(R) source 71 via the switch 135 and the CECline 84, and determines that the channel information has been received.

On the other hand, in the case that the HDMI(R) source 71 does not havea function for executing full-duplex communication, the channelinformation is not transmitted from the HDMI(R) source 71 to the HDMI(R)sink 72, and accordingly, the HDMI(R) sink 72 determines that no channelinformation has been received.

In the case that determination is made in step S115 that the channelinformation has been received, the processing proceeds to step S116,where the switching control unit 172 controls the switch 185 and theswitch 186 to switch the switch 185 and the switch 186 so as to selectthe differential signal corresponding to the Rx data from the conversionunit 184 at the time of transmitting data.

In step S117, the switching control unit 124 controls the switch 135 toswitch the switch 135 so as to select the differential signalcorresponding to the Tx data from the transmitter 81 at the time ofreceiving data.

In step S118, each unit of the HDMI(R) sink 72 executes two-way IPcommunication with the HDMI(R) source 71 by the full-duplexcommunication method, and the communication processing ends.Specifically, the conversion unit 184 converts the Rx data supplied fromthe HDMI(R) sink 72 into a differential signal, supplies one of thepartial signals making up the differential signal obtained by conversionto the switch 185, and supplies the other partial signal to the switch186, at the time of transmitting data. The switch 185 and the switch 186transmit the partial signal supplied from the conversion unit 184 to thetransmitter 81 via the SDA line 191 and the SCL line 192. Thus, thedifferential signal corresponding to the Rx data is transmitted from theHDMI(R) sink 72 to the HDMI(R) source 71.

Also, the decoding unit 136 receives the differential signalcorresponding to the Tx data transmitted from the transmitter 81 at thetime of receiving data. That is to say, the switch 135 receives thepartial signal of the differential signal corresponding to the Tx data,transmitted from the transmitter 81 via the CEC line 84, and suppliesthe received partial signal to the decoding unit 136. The decoding unit136 decodes the differential signal made up of the partial signalsupplied from the switch 135, and the partial signal supplied from thetransmitter 81 via the signal line 141 to Tx data that is the originaldata, and outputs this to the HDMI(R) sink 72.

Thus, the HDMI(R) sink 72 executes exchange of various types of datawith the HDMI(R) source 71, such as control data, pixel data, audiodata, and the like.

Also, in the case that determination is made in step S115 that nochannel information has been received, in step S119 each unit of theHDMI(R) sink 72 executes transmission/reception of the CEC signal,thereby executing two-way communication with the HDMI(R) source 71, andthe communication processing ends.

Thus, upon receiving the channel information, the HDMI(R) sink 72executes full-duplex communication with the HDMI(R) sink 72 using theCEC line 84 and the signal line 141, and the SDA line 191 and the SCLline 192.

Thus, the HDMI(R) sink 72 switches the switch 135, switch 185, andswitch 186 to select data to be transmitted and data to be received, andexecutes full-duplex communication with the HDMI(R) source 71 using theCEC line 84 and the signal line 141, and the SDA line 191 and the SCLline 192, whereby high-speed two-way communication can be executed whilemaintaining compatibility with the conventional HDMI(R).

Note that, with the example in FIG. 7, the HDMI(R) source 71 has beenconfigured wherein the conversion unit 131 is connected to the CEC line84 and the signal line 141, and the decoding unit 183 is connected tothe SDA line 191 and the SCL line 192, but may be configured wherein thedecoding unit 183 is connected to the CEC line 84 and the signal line141, and the conversion unit 131 is connected to the SDA line 191 andthe SCL line 192.

In such a case, the switch 181 and the switch 182 are connected to theCEC line 84 and the signal line 141, and are also connected to thedecoding unit 183, and the switch 133 is connected to the SDA line 191,and is also connected to the conversion unit 131.

Also, in the same way regarding the HDMI(R) sink in FIG. 7, anarrangement may be made wherein the conversion unit 184 is connected tothe CEC line 84 and the signal line 141, and the decoding unit 136 isconnected to the SDA line 191 and the SCL line 192. In such a case, theswitch 185 and the switch 186 are connected to the CEC line 84 and thesignal line 141, and are also connected to the conversion unit 184, andthe switch 135 is connected to the SDA line 191, and is also connectedto the decoding unit 136.

Further, in FIG. 6, the CEC line 84 and the signal line 141 may be takenas the SDA line 191 and the SCL line 192. That is to say, an arrangementmay be made wherein the conversion unit 131 and the decoding unit 132 ofthe HDMI(R) source 71, and the conversion unit 134 and the decoding unit136 of the HDMI(R) sink 72 are connected to the SDA line 191 and the SCLline 192, and the HDMI(R) source 71 and the HDMI(R) sink 72 executes IPcommunication by the half-duplex communication method. Further, in thiscase, connection of an electronic device may be detected using areserved pin of the connector to which the signal line 141 is connected.

Further, each of the HDMI(R) source 71 and the HDMI(R) sink 72 may haveboth of a function for executing half-duplex communication, and afunction for executing full-duplex communication. In such a case, theHDMI(R) source 71 and the HDMI(R) sink 72 can execute IP communicationby the half-duplex communication method or the full-duplex communicationmethod according to the function that the connected electronic devicehas.

In the case that each of the HDMI(R) source 71 and the HDMI(R) sink 72has both of a function for executing half-duplex communication, theHDMI(R) source 71 and the HDMI(R) sink 72 are configured such as shownin FIG. 14, for example. Note that, in FIG. 14, the portionscorresponding to those in the case of FIG. 6 and FIG. 7 are denoted withthe same reference numerals, and description thereof will be omitted.

The HDMI(R) source 71 shown in FIG. 14 is configured of a transmitter81, a switching control unit 121, a timing control unit 122, and aswitching control unit 171, and a conversion unit 131, a decoding unit132, a switch 133, a switch 181, a switch 182, and a decoding unit 183are provided to the transmitter 81. That is to say, the HDMI(R) source71 in FIG. 14 is configured wherein the timing control unit 122 and thedecoding unit 132 in FIG. 6 are further provided to the HDMI(R) source71 shown in FIG. 7.

Also, the HDMI(R) sink 72 shown in FIG. 14 is configured of a receiver82, a timing control unit 123, a switching control unit 124, and aswitching control unit 172, and a conversion unit 134, a switch 135, adecoding unit 136, a conversion unit 184, a switch 185, and a switch 186are provided to the receiver 82. That is to say, the HDMI(R) sink 72 inFIG. 14 is configured wherein the timing control unit 123 and theconversion unit 134 in FIG. 6 are further provided to the HDMI(R) sink72 shown in FIG. 7.

Next, the communication processing by the HDMI(R) source 71 and theHDMI(R) sink 72 in FIG. 14 will be described.

First, description will be made regarding the communication processingby the HDMI(R) source 71 in FIG. 14 with reference to the flowchart inFIG. 15. Note that the processes in step S151 through step S154 are thesame as the processes in step S71 through step S74 in FIG. 12respectively, and accordingly, description thereof will be omitted.

In step S155, the HDMI(R) source 71 determines whether or notfull-duplex communication with the HDMI(R) sink 72 is available. That isto say, the HDMI(R) source 71 references the E-EDID received from theHDMI(R) sink 72 to determine whether or not the full-duplex flag “FullDuplex” in FIG. 9 has been set.

In the case that determination is made in step S155 that full-duplexcommunication is available, i.e., in the case that the HDMI(R) sink 72shown in FIG. 14 or FIG. 7 is connected to the HDMI(R) source 71, instep S156 the switching control unit 171 controls the switch 181 and theswitch 182 to switch the switch 181 and the switch 182 so as to selectthe differential signal corresponding to the Rx data from the receiver82 at the time of receiving data.

On the other hand, in the case that determination is made thatfull-duplex communication is not available, in step S157 the HDMI(R)source 71 determines whether or not half-duplex communication isavailable. That is to say, the HDMI(R) source 71 references the receivedE-EDID to determine whether or not the half-duplex flag “Half Duplex” inFIG. 9 has been set. In other words, the HDMI(R) source 71 determineswhether or not the HDMI(R) sink 72 shown in FIG. 6 has been connected tothe HDMI(R) source 71.

In the case that determination is made in step S157 that half-duplexcommunication is available, or in the case that the switch 181 and theswitch 182 have been switched in step S156, in step S158 the HDMI(R)source 71 transmits the channel information to the receiver 82 via theswitch 133 and the CEC line 84.

Here, in the case that determination is made in step S155 thatfull-duplex communication is available, the HDMI(R) sink 72 has afunction for executing full-duplex communication, and accordingly, theHDMI(R) source 71 transmits a signal to the effect that IP communicationusing the CEC line 84 and the signal line 141, and the SDA line 191 andthe SCL line 192 is executed to the receiver 82 via the switch 133 andthe CEC line 84 as the channel information.

Also, in the case that determination is made in step S157 thathalf-duplex communication is available, the HDMI(R) sink 72 has nofunction for executing full-duplex communication, but has a function forexecuting half-duplex communication, and accordingly, the HDMI(R) source71 transmits a signal to the effect that IP communication using the CECline 84 and the signal line 141 is executed to the receiver 82 via theswitch 133 and the CEC line 84 as the channel information.

In step S159, the switching control unit 121 controls the switch 133 toswitch the switch 133 so as to select the differential signalcorresponding to the Tx data from the conversion unit 131 at the time oftransmitting data, and so as to select the differential signalcorresponding to the Rx data transmitted from the receiver 82 at thetime of receiving data. Note that, in the case that the HDMI(R) source71 and the HDMI(R) sink 72 execute full-duplex communication, thedifferential signal corresponding to the Rx data is not transmitted fromthe receiver 82 via the CEC line 84 and signal line 141 at the time ofthe HDMI(R) source 71 receiving data, and accordingly, the differentialsignal corresponding to the Rx data is not supplied to the decoding unit132.

In step S160, each unit of the HDMI(R) source 71 executes two-way IPcommunication with the HDMI(R) sink 72, and the communication processingends.

Specifically, in the case that the HDMI(R) source 71 and the HDMI(R)sink 72 execute full-duplex communication, and in the case of executinghalf-duplex communication, the conversion unit 131 converts the Tx datasupplied from the HDMI(R) source 71 into a differential signal, andtransmits one of the partial signal making up the differential signalobtained by conversion to the receiver 82 via the switch 133 and the CECline 84, and transmits the other partial signal to the receiver 82 viathe signal line 141, at the time of transmitting data.

Also, in the case that the HDMI(R) source 71 and the HDMI(R) sink 72execute full-duplex communication, the decoding unit 183 receives thedifferential signal corresponding to the Rx data transmitted from thereceiver 82, decodes the received differential signal to Rx data that isthe original data, and outputs this to the HDMI(R) source 71, at thetime of receiving data.

On the other hand, in the case that the HDMI(R) source 71 and theHDMI(R) sink 72 execute half-duplex communication, the decoding unit 132receives the differential signal corresponding to the Rx datatransmitted from the receiver 82 based on the control of the timingcontrol unit 122, decodes the received differential signal to Rx datathat is the original data, and outputs this to the HDMI(R) source 71, atthe time of receiving data.

Thus, the HDMI(R) source 71 executes exchange of various types of datawith the HDMI(R) sink 72, such as control data, pixel data, audio data,and the like.

Also, in the case that determination is made in step S157 thathalf-duplex is not available, in step S161 each unit of the HDMI(R)source 71 executes transmission/reception of the CEC signal, therebyexecuting two-way communication with the HDMI(R) sink 72 via the CECline 84, and the communication processing ends.

Thus, the HDMI(R) source 71 references the full-duplex flag and thehalf-duplex flag to execute full-duplex communication or half-duplexcommunication according to the function that the HDMI(R) sink 72 whichis a communication partner has.

Thus, the HDMI(R) source 71 switches the switch 133, switch 181, andswitch 182 to select data to be transmitted and data to be received, andexecutes full-duplex communication or half-duplex communication,according to the function that the HDMI(R) sink 72 which is acommunication partner has, whereby high-speed two-way communication canbe executed by selecting a more appropriate communication method whilemaintaining compatibility with the conventional HDMI(R).

Next, the communication processing by the HDMI(R) sink 72 in FIG. 14will be described with reference to the flowchart in FIG. 16. Note thatthe processes in step S191 through step S194 are the same as theprocesses in step S111 through step S114 in FIG. 13 respectively, andaccordingly, description thereof will be omitted.

In step S195, the HDMI(R) sink 72 receives the channel informationtransmitted from the HDMI(R) source 71 via the switch 135 and the CECline 84. Note that, in the case that the HDMI(R) source 71 connected tothe HDMI(R) sink 72 has neither a function for executing full-duplexcommunication nor a function for executing half-duplex communication, nochannel information is transmitted from the HDMI(R) source 71 to theHDMI(R) sink 72, and accordingly, the HDMI(R) sink 72 does not receivethe channel information.

In step S196, the HDMI(R) sink 72 determines whether or not full-duplexcommunication is executed, based on the received channel information.For example, in the case of receiving the channel information to theeffect that IP communication using the CEC line 84 and the signal line141, and the SDA line 191 and the SCL line 192 is executed, the HDMI(R)sink 72 determines that full-duplex communication is executed.

In the case that determination is made in step S196 that full-duplexcommunication is executed, in step S197 the switching control unit 172controls the switch 185 and the switch 186 to switch the switch 185 andthe switch 186 so as to select the differential signal corresponding tothe Rx data from the conversion unit 184 at the time of transmittingdata.

Also, in the case that determination is made in step S196 thatfull-duplex communication is not executed, in step S198 the HDMI(R) sink72 determines based on the received channel information whether or nothalf-duplex communication is executed. For example, in the case ofreceiving channel information to the effect that IP communication usingthe CEC line 84 and the signal line 141 is executed, the HDMI(R) sink 72determines that half-duplex communication is executed.

In the case that determination is made in step S198 that half-duplexcommunication is executed, or in the case that the switch 185 and theswitch 186 have been switched in step S197, the switching control unit124 controls the switch 135 to switch the switch 135 so as to select thedifferential signal corresponding to the Rx data from the conversionunit 134 at the time of transmitting data, and so as to select thedifferential signal corresponding to the Tx data from the transmitter 81at the time of receiving data.

Note that, in the case that the HDMI(R) source 71 and the HDMI(R) sink72 execute full-duplex communication, the differential signalcorresponding to the Rx data is not transmitted from the conversion unit134 to the transmitter 81 at the time of the HDMI(R) sink 72transmitting data, and accordingly, the differential signalcorresponding to the Rx data is not supplied to the switch 135.

In step S200, each unit of the HDMI(R) sink 72 executes two-way IPcommunication with the HDMI(R) source 71, and the communicationprocessing ends.

Specifically, in the case that the HDMI(R) source and the HDMI(R) sink72 execute full-duplex communication, at the time of transmitting data,the conversion unit 184 converts the Rx data supplied form the HDMI(R)sink 72 into a differential signal, transmits one of the partial signalsmaking up the differential signal obtained by conversion to thetransmitter 81 via the switch 185 and the SDA line 191, and transmitsthe other partial signal to the transmitter 81 via the switch 186 andSCL line 192.

Also, in the case that the HDMI(R) source 71 and the HDMI(R) sink 72execute half-duplex communication, at the time of transmitting data, theconversion unit 134 converts the Rx data supplied from the HDMI(R) sink72 into a differential signal, transmits one of the partial signalsmaking up the differential signal obtained by conversion to thetransmitter 81 via the switch 135 and the CEC line 84, and transmits theother partial signal to the transmitter 81 via the signal line 141.

Further, in the case that the HDMI(R) source 71 and the HDMI(R) sink 72execute full-duplex communication, and in the case of executinghalf-duplex communication, the decoding unit 136 receives thedifferential signal corresponding to the Tx data transmitted from thetransmitter 81, decodes the received differential signal to Tx data thatis the original data, and outputs this to the HDMI(R) sink 72, at thetime of receiving data.

Also, in the case that determination is made in step S198 thathalf-duplex communication is not executed, i.e., in the case that nochannel information has been transmitted, in step S201 each unit of theHDMI(R) sink 72 executes transmission/reception of the CEC signal,thereby executing two-way communication with the HDMI(R) source 71, andthe communication processing ends.

Thus, the HDMI(R) sink 72 executes full-duplex communication orhalf-duplex communication according to the received channel information,i.e., according to the function that the HDMI(R) source 71 which is acommunication partner has.

Thus, the HDMI(R) sink 72 switches the switch 135, switch 185, andswitch 186 to select data to be transmitted and data to be received, andexecutes full-duplex communication or half-duplex communication,according to the function that the HDMI(R) source 71 which is acommunication partner, whereby high-speed two-way communication can beexecuted by selecting a more appropriate communication method whilemaintaining compatibility with the conventional HDMI(R).

Also, the HDMI(R) source 71 and the HDMI(R) sink 72 are connected withthe HDMI(R) cable 35 including the CEC line 84 and the signal line 141which are connected mutually as a differential twist pair and groundedwith the ground line, and the SDA line 191 and the SCL line 192 whichare connected mutually as a differential twist pair and grounded withthe ground line, whereby high-speed two-way IP communication can beexecuted by the half-duplex communication method or full-duplexcommunication method while maintaining compatibility with theconventional HDMI(R) cable.

As described above, one of a single or multiple pieces of data to betransmitted is selected as data to be transmitted, the selected data istransmitted to a communication partner via a predetermined signal line,one of a single or multiple pieces of data to be received, transmittedfrom the communication partner, is selected as data to be received, andthe selected data is received, whereby compatibility serving as HDMI(R)is maintained between the HDMI(R) source 71 and the HDMI(R) sink 72,i.e., the pixel data of an uncompressed image can be transmitted fromthe HDMI(R) source 71 to the HDMI(R) sink 72 at high speed in onedirection, and also high-speed two-way IP communication can be executedvia the HDMI(R) cable 35.

As a result thereof, in the case that a source device which is anelectronic device such as the playback device 33 in FIG. 2 or the like,having the HDMI(R) source 71 built-in, has a server function such asDLNA (Digital Living Network Alliance) or the like, and a sink devicewhich is an electronic device such as the digital television receiver 31in FIG. 2 or the like, having the HDMI(R) sink 72 built-in, has acommunication interface for LAN such as Ethernet (Registered Trademark)or the like, for example, according to two-way IP communication via anelectronic device such as the amplifier 32 connected directly or via anHDMI(R) cable, or the like, a content can be transmitted from the sourcedevice to the sink device via the HDMI(R) cable, and further, thecontent from the source device can be transmitted from the sink deviceto another device connected to the communication interface for LAN ofthe sink device (e.g., digital television receiver 34 in FIG. 2, or thelike).

Further, according to two-way IP communication between the HDMI(R)source 71 and the HDMI(R) sink 72, a command or response for control canbe exchanged at high speed between the source device having the HDMI(R)source 71 built-in, and the sink device having the HDMI(R) sink 72built-in, which are connected with the HDMI(R) cable 35, therebyenabling control between devices having fast response.

The above series of processing can be executed not only by a dedicatedhardware but also by software. In the case of executing the series ofprocessing by software, a program making up the software thereof isinstalled in, for example, a microcomputer for controlling the HDMI(R)source 71 or HDMI(R) sink 72, or the like.

Therefore, FIG. 17 illustrates a configuration example of an embodimentof a computer in which the program for executing the above series ofprocessing is installed.

The program may be recorded in EEPROM (Electrically ErasableProgrammable Read-only Memory) 305 or ROM 303 serving as a recordingmedium built in the computer beforehand.

Alternatively, the program may be temporarily or permanently stored in aremovable recording medium such as a flexible disk, CD-ROM (Compact DiscRead Only Memory), MO (Magnetic Optical) disk, DVD (Digital VersatileDisc), magnetic disk, semiconductor memory, or the like. Such aremovable recording medium may be provided as so-called packagedsoftware.

Note that the program may be transferred to the computer wirelessly viaa satellite for digital satellite broadcasting from a download cite, ormay be transferred to the computer by cable via a network such as a LAN,the Internet, or the like, in addition to being installed in thecomputer from a removable recording medium such as described above, andthe computer may receive the program thus transferred at an input/outputinterface 306 to install this in the built-in EEPROM 305.

The computer has the CPU (Central Processing Unit) 302 built-in. The CPU302 is connected to the input/output interface 306 via a bus 301, andthe CPU 302 loads the program stored in the ROM (Read Only Memory) 303or EEPROM 305 to RAM (Random Access Memory) 304, and executes this.Thus, the CPU 302 executes the processing in accordance with the aboveflowcharts, or processing executed with the configuration of the aboveblock diagram.

Now, with the present Specification, the processing steps describing theprogram for causing the computer to execute various types of processingdo not necessarily have to be processed in time-sequence following theorder laid forth as flowcharts, and include processing executed inparallel or individually (e.g., parallel processing or processing byobjects).

Also, the program may be processed by a single computer, or may beprocessed in a distributed manner by multiple computers.

Note that the present invention may be applied to, in addition toHDMI(R), a communication interface made up of a transmission deviceconfigured to transmit the differential signal corresponding to thepixel data of one screen worth of an uncompressed image to a receptiondevice in one direction using multiple channels during a valid imagesection that is a section obtained by removing a horizontal retracesection and a vertical retrace section from a section between onevertical synchronizing signal and the next vertical synchronizingsignal, and the reception device configured to receive the differentialsignal transmitted from the transmission device with the multiplechannels.

Also, with the present embodiment, though two-way IP communication hasbeen executed by controlling data selecting timing, differential signalreceiving timing, and transmission timing between the HDMI(R) source 71and the HDMI(R) sink 72 as appropriate, two-way communication may beexecuted with a protocol other than IP.

Note that the embodiments of the present invention are not restricted tothe above embodiment, and various modifications can be performed withoutdeparting from the essence of the present invention.

According to the above embodiment, two-way communication can beexecuted. Specifically, for example, with a communication interfacecapable of transmitting the pixel data of an uncompressed image, andaudio data accompanying the image thereof at high speed in onedirection, high-speed two-way communication can be executed whilemaintaining compatibility.

Incidentally, though there are portions overlapped with the alreadydescribed techniques, many of video audio devices are installing a LANcommunication function for a purpose such as two-way program viewing,advanced remote control, reception of an electronic program guide, orthe like.

As means for forming the network thereof between video audio devices,there are choices such as laying of a dedicated cable such as CAT5,wireless communication, power line communication, and the like.

However, these choices have a disadvantage such that a dedicated cablemakes connection between devices cumbersome and complicated, andwireless or power line connection makes a modulation circuit and atransmitter/receiver complicated and expensive.

Therefore, with the above embodiment, a technique for adding a LANcommunication function to the HDM without adding a new connectorelectrode thereto has been disclosed.

HDMI is an interface for executing transmission of video and audio data,exchange and authentication of connected device information, andcommunication of device control data using a single cable, andaccordingly, it is advantageous to enable LAN communication withoutusing a dedicated cable, wireless, or the like, by adding a LAN functionthereto.

Incidentally, with the technique disclosed as the above embodiment, adifferential transmission path used for LAN communication is also usedfor exchange and authentication of connected device information, andcommunication of device control data.

With HDMI, the connected device electric property is strictly restrainedin respect of parasitic capacitance or impedance regarding a DDC forexecuting exchange and authentication of connected device information,and CEC for executing communication of device control data.

Specifically, the DDC terminal parasitic capacitance of a device has tobe equal to or smaller than 50 pF, and the DDC terminal has to begrounded with ground GND of which the impedance is 200Ω at the time ofLOW output, and has to be pulled up with power supply of which theimpedance is 2 kΩ or so in a HIGH state.

On the other hand, with LAN communication for propagating a high-speedsignal, the transmission/reception terminal has to be terminated with100Ω or so at least at a high-frequency band to stabilize communication.In order to satisfy the parasitic capacitance constraint of the DDC, LANtransmission and reception circuits to be added to the DDC line has tohave AC connection via sufficient small capacitance, a LAN signal isattenuated greatly and subjected to distortion, and accordingly, thereis a possibility that the transmission and reception circuits forcompensating this may be complicated and high in cost.

Also, with the DDC communication, there is a possibility that transitionbetween HIGH and LOW states may disturb LAN communication. That is tosay, there is a possibility that the LAN may not function during a DDCcommunication period.

Therefore, description will be made below as a further suitableembodiment regarding a communication system having features wherein,with an interface for executing transmission of video and audio data,exchange and authentication of connected device information,communication of device control data, and LAN communication using asingle cable, LAN communication is executed with two-way communicationvia one pair of differential transmission paths, and the connectionstate of the interface is notified with the DC bias potential of atleast one of the transmission paths.

With the technique described below, the selecting unit does notnecessarily have to be provided such as the above embodiment.

FIG. 18 is a circuit diagram illustrating a first configuration exampleof a communication system of which the interface connection state isnotified with the DC bias potential of at least one of the transmissionpaths.

FIG. 19 is a diagram illustrating a configuration example of a system inthe case of implementing Ethernet (Registered Trademark) (Ethernet(Registered Trademark)).

This communication system 400 is configured, such as shown in FIG. 18and FIG. 19, so as to include a LAN expansion HDMI(hereafter, EH) sourcedevice 401, an EH sink device 402, an EH cable 403 for connecting an EHsource device and an EH sink device, an Ethernet (Registered Trademark)transceiver 404, and an Ethernet (Registered Trademark) receiver 405.

The EH source device 401 includes a LAN signal transmission circuit 411,a terminating resistor 412, AC connection capacities 413 and 414, a LANsignal reception circuit 415, a subtracting circuit 416, a pull-upresistor 421, a resistor 422 and a capacitance 423 making up a low-passfilter, a comparator 424, a pull-down resistor 431, a resistor 432 and acapacitance 433 making up a low-pass filter, and a comparator 434.

The EH sink device 402 includes a LAN signal transmission circuit 441, aterminating resistor 442, AC connection capacities 443 and 444, a LANsignal reception circuit 445, a subtraction circuit 446, a pull-downresistor 451, a resistor 452 and a capacitance 453 making up a low-passfilter, a comparator 454, a choke coil 461, and resistors 462 and 463serially connected between the power supply potential and the referencepotential.

There is a differential transmission path made up of a reserved line 501and an HPD line 502, the source-side terminal 511 of the reserved line501 and the source-side terminal 512 of the HDP line 502, and thesink-side terminal 521 of the reserved line 501 and the sink-sideterminal 522 of the HDP line are formed, within the EH cable 403. Thereserved line 501 and the HPD line 502 are connected as a differentialtwist pair.

With the communication system 400 thus configured, the terminal 511 andthe terminal 512 are connected to the terminating resistor 412, LANsignal transmission circuit 411, and LAN signal reception circuit 415via the AC connection capacities 413 and 414 within the source device401.

The subtracting circuit 416 receives a sum signal SG412 of atransmission signal voltage that the current output from the LAN signaltransmission circuit 411 generates with the terminating resistor 412 andthe transmission paths 501 and 502 as load, and a reception signalvoltage that is a signal transmitted from the EH sink device 402.

With the subtracting circuit 416, a signal SG413 obtained by subtractinga transmission signal SG411 from the sum signal SG412 is a net signaltransmitted from the sink.

There is a similar circuit network within the sink device 402, and thesource device 4011 and the sink device 4022 execute two-way LANcommunication using these circuits.

Also, the HDP line 502 notifies the source device 401 that the cable 403is connected to the sink device 402 with a DC bias level in addition tothe above LAN communication.

Upon the cable 403 being connected to the sink device 402, the resistors462 and 463 and the choke coil 461 within the sink device 402 bias theHDP line 502 to around 4 V via the terminal 522.

The source device 401 extracts the DC bias of the HPD line 502 at thelow-pass filter made up of the resistor 432 and the capacitance 433, andcompares this with a reference potential Vref2 (e.g., 1.4 V) at thecomparator 434.

In the event that the cable 403 is not connected to the source device402, the potential of the terminal 512 is lower than the referencepotential Vref2 at the pull-down resistor 431, and in the event of beingconnected, the potential thereof is higher than the reference potentialVref2.

Accordingly, in the event that the output signal SG415 of the comparator434 is HIGH, this indicates that the cable 403 is connected to the sinkdevice 402.

On the other hand, in the event that the output signal SG415 of thecomparator 434 is LOW, this indicates that the cable 403 is notconnected to the sink device 402.

The present first configuration example further has a function formutually recognizing whether the device connected to both ends of thecable 4033 with the DC bias potential of the reserved line 501 is anEH-compatible device or incompatible HDMI device.

The EH source device 401 pulls up the reserved line 501 with theresistor 421 (+5V), and the EH sink device 402 pulls down this with theresistor 451.

These resistors 421 and 451 are not included in an EH-incompatibledevice.

The EH source device 401 compares the DC potential of the reserved line501 passed through the low-pass filter made up of the resistor 422 andthe capacitance 423 with the reference voltage Vref1 at the comparator424.

When the sink device 402 is compatible with EH and has pull-down, thepotential of the reserved line 501 is 2.5 V, and when the sink device402 is incompatible and open, the potential is 5 V, and accordingly,compatibility/incompatibility of the sink device can be recognized ifthe reference voltage Vref1 is set to 3.75 V.

The sink device 402 compares the DC potential of the reserved line 501passed through the low-pass filter made up of the resistor 452 and thecapacitance 453 with a reference voltage Vref3 at the comparator 454.

In the event that the source device 402 is compatible with EH and has apull-up function, the DC potential of the reserved line 501 is 2.5 V,and in the event of incompatible, is 0 V, and accordingly,EH-compatibility/incompatibility of the source device can be recognizedif the reference potential is set to 1.25 V.

Thus, according to the present first configuration example, with aninterface for executing transmission of video and audio data, exchangeand authentication of connected device information, communication ofdevice control data, and LAN communication using a single cable 403, LANcommunication is executed with two-way communication via one pair ofdifferential transmission paths, and the connection state of theinterface is notified with the DC bias potential of at least one of thetransmission paths, and accordingly, spatial separation using neitherthe SCL line nor the SDA line for the sake of LAN communicationphysically can be executed.

As a result thereof, a circuit for LAN communication can be formedaccording to the separation thereof regardless of electrical standardsstipulated regarding the DDC, and stable sure LAN communication can berealized inexpensively.

FIG. 20 is a circuit diagram illustrating a second configuration exampleof a communication system wherein the connection state of the interfaceis notified with the DC bias potential of at least of the transmissionpaths.

This communication system 600 has, basically similar to the firstconfiguration example, a configuration wherein, with an interface forexecuting transmission of video and audio data, exchange andauthentication of connected device information, communication of devicecontrol data, and LAN communication using a single cable, LANcommunication is executed with one-way communication via two pairs ofdifferential transmission paths, and the connection state of theinterface is notified with the DC bias potential of at least one of thetransmission paths, and further, has a feature wherein at least twotransmission paths are used for communication of exchange andauthentication of connected device information in a manner time-sharingwith LAN communication.

This communication system 600 is configured so as to include a LANfunction expansion HDMI (hereafter, EH) source device 601, an EH sinkdevice 602, and an EH cable 603 for connecting an EH sink device and anEH sink device.

The EH source device 601 includes a LAN signal transmission circuit 611,terminating resistors 612 and 613, AC connection capacities 614 through617, a LAN signal reception circuit 618, an inverter 620, a resistor621, a resistor 622 and a capacitance 623 making up a low-pass filter, acomparator 624, a pull-down resistor 631, a resistor 632 and acapacitance 633 making up a low-pass filter, a comparator 634, a NORgate 640, analog switches 641 through 644, an inverter 645, an analogswitch 646 and 747, DDC transceivers 651 and 652, and pull-up resistors653 and 654.

The EH sink device 602 includes a LAN signal transmission circuit 661,terminating resistors 662 and 663, AC connection capacities 664 through667, a LAN signal reception circuit 668, a pull-down resistor 671, aresistor 672 and a capacitance 673 making up a low-pass filter, acomparator 674, a choke coil 681, resistors 682 and 683 seriallyconnected between the power supply potential and the referencepotential, analog switches 691 through 694, an inverter 695, analogswitches 696 and 697, DDC transceivers 701 and 702, and pull-upresistors 703 and 704.

There is a differential transmission path made up of a reserved line 801and an SCL line 803, and a differential transmission path made up of anSDA line 804 and an HDP line 802, and the source-side terminal 811through 814 thereof, and the sink-side terminals 821 through 824 areformed, within the EH cable 603.

The reserved line 801 and the SCL line 803, and the SDA line 804 and theHPD line 802 are connected as a differential twist pair.

With the communication system 600 thus configured, the terminals 811 and813 are connected to the transmission circuit 611 for transmitting a LANtransmission signal SG611 to the sink, and the terminating resistor 612via the AC connection capacities 614 and 605 and the analog switches 641and 642 within the source device 603.

The terminals 814 and 812 are connected to the reception circuit 618 forreceiving the LAN signal from the sink device 602, and the terminatingresistor 613 via the AC connection capacities 616 and 617, and theanalog switches 6433 and 644.

The terminals 821 through 824 are connected to the transmission andreception circuits 668 and 661 and the terminating resistors 662 and 663via the AC connection capacities 664, 665, 666, and 667, and the analogswitches 691 through 694 within the sink device 602.

The analog switches 641 through 644, and 691 through 694 areelectrically conducted when executing LAN communication, and are openedwhen executing DDC communication.

The source device 601 connects the terminal 813 and the terminal 814 tothe DDC transceivers 651 and 652, and the pull-up resistors 653 and 654via other analog switches 646 and 647.

The sink device 602 connects the terminal 823 and the terminal 824 tothe DDC transceivers 701 and 702, and the pull-up resistor 703 via theanalog switches 696 and 697.

The analog switches 646 and 647 are electrically conducted whenexecuting DDC communication, and are opened when executing DLANcommunication.

The EH-compatible device recognizing mechanism according to thepotential of the reserved line 801 is basically the same as with thecase of the first configuration example except that the resistor 62 ofthe source device 601 is driven by the inverter 620.

The resistor 621 becomes a pull-down resistor when the input of theinverter 620 is HIGH, and accordingly, this goes into the same 0 V stateas with the case of being connected to an EH-incompatible device asviewed from the sink device 602.

As a result thereof, a signal SG623 indicating the EH-compatibilitydetermination result of the sink device 602 becomes LOW, the analogswitches 691 through 694 controlled by the signal SG623 are opened, andthe analog switches 696 and 697 controlled by a signal obtained byinverting the signal SG623 at the inverter 695 are electricallyconducted.

As a result thereof, the sink device 602 separates the SCL line 803 andthe SDA line 804 from the LAN transmitter and receiver, and goes into astate of being connected to the DDC transmitter and receiver.

On the other hand, with the source device 601, the input of the inverter620 is also input to the NOR gate 640 to set an output SG614 thereof toLOW.

The analog switches 641 through 644 controlled by the output signalSG614 of the NOR gate 640 are opened, and the analog switches 646 and647 controlled by a signal obtained by inverting the signal SG614 at theinverter 645 are electrically conducted.

As a result thereof, the source device 601 also separates the SCL line803 and the SDA line 804 from the LAN transmitter and receiver, and goesinto a state of being connected to the DDC transmitter and receiver.

Conversely, when the input of the inverter 620 is LOW, the source device601 and the sink device 602 separate the SCL line 803 and the SDA line804 from the DDC transmitter and receiver, and go into a state of beingconnected to the LAN transmitter and receiver.

The circuits 631 through 634, and 681 through 683 for confirmingconnection according to the DC bias potential of the HPD line 802 havethe same function as those in the first configuration example.

Specifically, the HPD line 802 notifies the source device 601 that thecable 803 has been connected to the sink device 602 with a DC bias levelin addition to the above LAN communication.

Upon the cable 803 being connected to the sink device 602, the resistors682 and 683 and the choke coil 681 within the sink device 602 bias theHPD line 802 to around 4 V via the terminal 822.

The source device 601 extracts the DC bias of the HPD line 802 at thelow-pass filter made up of the resistor 632 and the capacitance 633, andcompares this with the reference potential Vref2 (e.g., 1.4 V) at thecomparator 634.

In the event that the cable 803 is not connected to the source device602, the potential of the terminal 812 is lower than the referencepotential Vref2 with the pull-down resistor 631, and in the event ofbeing connected, the potential of the terminal 812 is higher than thereference potential Vref2.

Accordingly, in the event that the output signal SG613 of the comparator634 is HIGH, this indicates that the cable 803 and the sink device 602are connected.

On the other hand, in the event that the output signal SG613 of thecomparator 634 is LOW, this indicates that the cable 803 and the sinkdevice 602 are not connected.

Thus, according to the present second configuration example, anarrangement is provided wherein, with an interface for executingtransmission of video and audio data, exchange and authentication ofconnected device information, communication of device control data, andLAN communication using a single cable, LAN communication is executedwith one-way communication via two pairs of differential transmissionpaths, and the connection state of the interface is notified with the DCbias potential of at least one of the transmission paths, and further,at least two transmission paths are used for communication of exchangeand authentication of connected device information in a mannertime-sharing with LAN communication, whereby time sharing for dividingtime into a time zone for connecting the SCL line and the SDA line tothe LAN communication circuit by the switches, and a time zone forconnecting the SCL line and the SDA line to the DDC circuit, can beexecuted, circuits for LAN communication can be formed regardless ofelectrical standards stipulated regarding the DDC according to thisdivision, and stable sure LAN communication can be realizedinexpensively.

As described above, with the embodiment correlated with FIG. 2 throughFIG. 17, full-duplex communication is realized wherein one-waycommunication is executed with SDA and SCL of HDMI 19 poles as a firstdifferential pair, and one-way communication is executed with CEC andReserved as a second pair.

However, communication is executed with SDA and SCL wherein H is 1.5 kΩpull-up, and L is low-impedance pull-down, and with CEC and H wherein His 27 kΩ pull-up, and L is low-impedance pull-down.

Maintaining such functions while having compatibility with the existingHDMI may have difficulty in sharing a LAN function for executinghigh-speed data communication necessary for subjecting the terminationsof a transmission line to matching termination.

Therefore, with the first configuration example, an arrangement has beenmade wherein full-duplex communication by one pair two-way communicationis executed with Reserved and HPD as a differential pair by avoiding useof the SDA, SCL, and CEC lines.

HPD is a flag signal according to a DC level, and accordingly, both ofinfusion of a LAN signal according to AC connection, and transmission ofplug information according to a DC level hold. A function for mutuallyrecognizing that the terminal has a LAN function according to a DC levelusing a method similar to HPD is added to Reserved anew.

With the second configuration example, an arrangement is made whereintwo-pair full-duplex communication for executing one-way communicationis executed with each of two-pair differential pairs made up of HPD,SDA, SCL, and Reserved.

With HDMI, DDC communication in a burst manner according to SDA and SCLis executed wherein the transmitter becomes the master, and controls thetiming thereof.

With this example, when the transmitter executes DDC communication, theanalog switches are operated so as to connect the SDA, SCL lines to thetransceiver for DDC, and when the transmitter does not execute DDCcommunication, the analog switches are operated so as to connect thelines to the transceiver for LAN.

This switch operation signal is transmitted to the receiver with the DClevel of the Reserved line, and the same switch switching is executed onthe receiver side.

The above arrangement is employed, whereby, as a first advantage, theSCL, SDA, and CEC communication do not receive noise due to LANcommunication, and stable DDC and CEC communication can be securedconstantly.

With the first configuration example, this is achieved by separating LANfrom these lines physically, and with the second configuration example,this is achieved by disconnecting the LAN signal from the lines duringDDC communication using the switches.

As a second advantage, LAN communication is executed with a line havingideal terminations, whereby stable communication with a large margin canbe executed.

This is because, with the first configuration example, the LAN signal issuperimposed on the lines of Reserved and HPD where only a DC level istransmitted, and accordingly, termination impedance can be held with anideal value over sufficient wide frequencies necessary for LANcommunication, and with the second configuration example, a terminationcircuit for LAN which is not activated at the time of DDC communicationis connected only when executing LAN communication.

FIGS. 21(A) through (E) are diagrams illustrating a two-waycommunication waveform according to the communication system of thepresent configuration example.

FIG. 21(A) illustrates a signal waveform transmitted from the EH sourcedevice, FIG. 21(B) illustrates a signal waveform received at the EH sinkdevice, FIG. 21(C) illustrates a signal waveform passing through acable, FIG. 21(D) illustrates a signal received at the EH source device,and FIG. 21(E) illustrates a signal waveform transmitted from the EHsource device, respectively.

Such as shown in FIG. 21, according to the present configurationexample, excellent two-way communication can be realized.

With a system including multiple devices to be connected by using HDMIand Ethernet (Registered Trademark) together, a method for calculatingthe address of Ethernet (Registered Trademark) based on the uniqueaddress of each of the devices assigned at the time of HDMI connection,and the system employing this will be described below.

FIG. 22 is a diagram illustrating a system including multiple devices tobe connected by using HDMI and Ethernet (Registered Trademark) together.This system is configured of a device 901 through a device 904. With thedevice 901, an HDMI terminal 911 and an Ethernet (Registered Trademark)terminal 912 which make up a pair, an Ethernet (Registered Trademark)terminal 913, and an HDMI terminal 914 and an Ethernet (RegisteredTrademark) terminal 915 which make up a pair, are provided.

Also, with the device 902, an HDMI terminal 916 and an Ethernet(Registered Trademark) terminal 917 which make up a pair, is provided.The HDMI terminal 916 of the device 902, and the HDMI terminal 911 ofthe device 901 are connected with a cable or the like, and the Ethernet(Registered Trademark) terminal 917 of the device 902, and the Ethernet(Registered Trademark) terminal 912 of the device 901 are connected witha cable or the like.

Further, with the device 904, an Ethernet (Registered Trademark)terminal 918 is provided, and this Ethernet (Registered Trademark)terminal 918 is connected to the Ethernet (Registered Trademark)terminal 913 of the device 901 with a cable or the like. Further, anHDMI terminal 919 and an Ethernet (Registered Trademark) terminal 920which make up a pair are provided. The HDMI terminal 919 of the device903, and the HDMI terminal 914 of the device 901 are connected with acable or the like, and the Ethernet (Registered Trademark) terminal 920of the device 903, and the Ethernet (Registered Trademark) terminal 915of the device 901 are connected with a cable or the like.

Incidentally, with devices connected with HDMI, there is a function forexchanging a command message called CEC, Physical Address to be storedin an HDMI VSDB is used for determining the transmission side and thereception side thereof. This will be quoted from HDMI spec. 1.3a(High-Definition Multimedia Interface Specification Version 1.3a), andthe structure thereof will be shown below.

8.3.2 HDMI Vendor-Specific Data Block (HDMI VSDB)

The first CEA Extension shall include an HDMI Vendor Specific Data Block(HDMI VSDB) shown in Table 8-6. This is a CEA-861-D Vendor Specific DataBlock (see CEA-861-D section 7.5.4 for details) containing a 24-bit IEEERegistration Identifier of 0x000003, a value belonging to HDMILicensing, LLC.

Sinks shall contain an HDMI VSDB minimally containing a 2-byte SourcePhysical Address field following the 24-bit identifier. An HDMI VSDB mayhave zero or more extension fields as shown in Table 8-6. The minimumvalue of N (length) is 5 and the maximum value of N is 31. A Sink thatsupports any function indicated by an extension field shall use an HDMIVSDB with a length sufficient to cover all supported fields.

The Source shall have the ability to handle an HDMI VSDB of any length.In future specifications, new fields may be defined. These additionalfields will be defined such that a zero value indicates the samecharacteristics as is indicated if the field was not present. Sourceshould use the length field to determine which extension fields arepresent, and shall process the HDMI VSDB with no regard to non-zerovalues in fields defined as Reserved in this specification.

Now, FIG. 23 is a diagram illustrating Table 8-6 with the above HDMIspec. 1.3a. That is to say, FIG. 23 is a diagram illustrating HDMI VSDB.In FIG. 23, Physical Addresses are denoted with A, B, C, and D.

Specifically, let us say that the first CEA extension includes HDMIVendor-specific Data Block (HDMI VSDB) shown in Table 8-6 (FIG. 23).This is CEA-A-861-D Vendor-specific Data Block including a 24-bit IEEEregistration identifier of 0x000003, which is a value belonging to HDMILicensing, LLC (see CEA-861-D section 7.5.4 with regard to the details).

Let us say that sinks include an DHMI VSDB minimally including a 2-byteSource Physical Address field following the 24-bit identifier. An HDMIVSDB may have zero or more extension field such as shown in Table 8-6(FIG. 23). The minimum value of N (length) is 5, and the maximum valueof N is 31. Let us say that a sink supporting any function indicatedwith an extension field shall use an HDMI VSDB with a length sufficientfor covering all the fields to be supported.

Let us say that sources have capability to handle an HDMI VSDB of anylength. With future specifications, new fields may be defined. Theseadditional fields will be defined such that a zero value indicates thesame characteristics as is indicated if the field was not present.Sources have to use the length field to determine which extension fieldis present, and let us say that sources process an HCMI VSDB regardlessof values other than zero in fields defined as Reserved in the presentspecification.

Next, a method for determining this Physical Address will be shown belowby quoting HDMI spec. 1.3a.

8.7 Physical Address

8.7.1 Overview

In order to allow CEC to be able to address specific physical devicesand control switches, all devices shall have a physical address. Thisconnectivity has to be worked out whenever a new device is added to thecluster. The physical address discovery process uses only the DDC/EDIDmechanism and applies to all HDMI Sinks and Repeaters, not only toCEC-capable devices.

The CEC and DDC connections are shown in FIG. 8-1.

The CEC line is directly connected to all nodes on the network.

After discovering their own physical address, the CEC devices transmittheir physical and logical addresses to all other devices, thus allowingany device to create a map of the network.

8.7.2 Physical Address Discovery

The physical address of each node is determined through the physicaladdress discovery process. This process is dynamic in that itautomatically adjusts physical addresses as required as devices arephysically or electrically added or removed from the device tree.

All Sinks and Repeaters shall perform the steps of physical addressdiscovery and propagation even if those devices are not CEC-capable.Sources are not required to determine their own physical address unlessthey are CEC-capable.

All addresses are 4 digits long allowing for a 5device-deep hierarchy.All are identified in the form of n.n.n.n in the following description.An example of this is given in FIG. 8-3.

A Sink or Repeater that is acting as the CEC root device will generateits own physical address: 0.0.0.0. A source or a Repeater reads itsphysical address from the EDID of the connected Sink. The CEC line maybe connected to only the HDMI output so a device with multiple HDMIoutputs will read its physical address from the EDID on theCEC-connected output. Each Sink and Repeater is responsible forgenerating the physical address of all Source devices connected to thatdevice by appending a port number onto its own physical address andplacing that value in the EDID for that port. The Source Address Fieldof the HDMI Vendor Specific Data Block (see Section 8.3.2) is used forthis purpose.

Note that the values shown in the figures below represent the physicaladdresses for the devices themselves, not the Source physical addressesstored in the EDID within that device. In fact, for all devices shown,except the TV, those physical addresses are stored in the EDID of theconnected Sink. An example is shown for the TV at physical address0.0.0.0.

8.7.3 Discovery Algorithm

The following algorithm is used to allocate the physical address of eachdevice whenever HPD is de-asserted or upon power-up:

Disable assertion of HPD to all source devices If I am CEC root Setmy_address to 0.0.0.0 Else Wait for HPD from sink Query sink formy_address of my connection (Section 8.7.4) The device shall retain thisphysical address until HPD is removed (or the device is powered off).End if If device has connections for source devices then Label allpossible connections to source devices uniquely starting Fromconnection_label = 1 to the number of source input connections If devicehas separate EDIDs for each source connection then If my_address endswith 0 then Set each source_physical_address to my_address with thefirst 0 being replaced with connection_label. Else (i.e. beyond thefifth layer of the tree) Set each source_physical_address to F.F.F.F Endif Else Set each source_physical_address to my_address End if Writesource_physical_address to HDMI VSDB in EDID for each source connectionEnd if Allow HPD to be asserted for source devices

8.7.4 HDMI Sink Query

A Source shall determine its physical address (my_address) by checkingthe HDMI Vendor Specific Data Block (see Section 8.3.2) within the EDID.The fourth and fifth bytes of this 5 byte structure contain the SourcePhysical Address (fields A, B, C, D).

Now, FIG. 24 is a diagram illustrating “FIG. 8-1” in the above HDMIspec. 1.3a. That is to say, FIG. 24 is a diagram illustrating connectionof CEC and DDC. Also,

FIG. 25 is a diagram illustrating “FIG. 8-2” in the HDMI spec. 1.3a,i.e., a diagram illustrating HDMI cluster. Further, FIG. 26 is a diagramillustrating “FIG. 8-3” in the HDMI spec. 1.3a, i.e., a diagramillustrating HDMI cluster.

In order to allow CEC to be able to address specific physical devicesand control switches, all devices shall have a physical address. Thisconnectivity has to be taken into consideration regardless of whether ornot a new device is added to the cluster. The physical address discoveryprocess uses only the DDC/EDID mechanism and applies to all HDMI Sinksand Repeaters, not only to CEC-capable devices. The CEC and DDCconnections are shown in FIG. 24. The CEC line is directly connected toall the nodes on the network. After discovering their own physicaladdress, the CEC devices transmit their physical and logical addressesto all other devices, thus allowing any device to create a map of thenetwork.

Also, the physical address of each node is determined with the physicaladdress discovery process. This process is dynamic in that itautomatically adjusts the physical address as required such that devicesare physically or electrically added or removed from the device tree.Let us say that all Sinks and Repeaters execute the steps of physicaladdress discovery and propagation even if those devices are notCEC-capable. Sources are not required to determine their own physicaladdresses unless they are CEC-capable.

All addresses are 4 digits long allowing for a 5-device-depth hierarchy.All are identified in the form of n.n.n.n in the following description.An example of this is given in FIG. 26.

A Sink or Repeater that is acting as the CEC root device will generateits own physical address: 0.0.0.0. A source or a Repeater reads itsphysical address from the EDID of the connected Sink. The CEC line maybe connected to only a single HDMI output so a device with multiple HDMIoutputs will read its physical address from the EDID on theCEC-connected output. Each Sink and Repeater is responsible forgenerating the physical addresses of all Source devices connected tothat device by appending a port number onto its own physical address andplacing that value in the EDID for that port. The Source Address Fieldof the HDMI Vendor Specific Data Block (see Section 8.3.2) is used forthis purpose.

Note that the values shown in the FIG. 26 represent the physicaladdresses for the devices themselves, not the Source physical addressesstored in the EDID within that device. In fact, for all devices shown,except the TV, those physical addresses are stored in the EDID of theconnected Sink. An example is shown for the TV at physical address0.0.0.0.

Further, the above algorithm is used to allocate the physical address ofeach device whenever HPD is de-asserted or upon power-up.

Let us say that a Source determines its physical address (my_address) bychecking the HDMI Vendor-Specific Data Block within the EDID (seeSection 8.3.2). The fourth and fifth bytes of this 5-byte structureinclude the source physical address (fields A, B, C, D).

Also, with CEC, a logical address is determined such as the followingbased on the physical address obtained here. Hereafter, a method fordetermining a logical address will be shown by quoting the HDMI Spec.1.3a.

CEC is a protocol based on a bus system and therefore cannot aloneascertain the physical connectivity of the network. The mechanismdefined in section 8.7 uses DDC to allocate physical addresses todevices in the network.

All CEC devices therefore have both a physical and logical address,whereas non-CEC devices only have a physical address.

CEC 10.1 Physical Address Discovery

The algorithm defined in 8.7.3 is used to allocate the physical addressof each device.

Whenever a new physical address (other than F.F.F.F) is discovered, aCEC device shall:

allocate the logical address (see CEC 10.2.1)

report the association between its logical and physical addresses bybroadcasting <Report Physical Address>.

This process allows any node to create a map of physical connections tological addresses.

CEC 10.2 Logical Addressing

Each device appearing on the control signal line has a logical addresswhich is allocated to only one device in the system. This addressdefines a device type as well as being a unique identifier. These arespecified in CEC Table 5.

If a physical device contains the functions of more than one logicaldevice then it should take the logical addresses for each of thoselogical devices. For example, a if a DVD recorder has a tuner, it maytake one of the addresses 3, 6, 7, or 10 (Tuner) in addition to one of1, 2, or 9 (Recording Device).

It is allowed for a device to declare the functionality of anotherdevice by using a different logical address. For example, a recordableDVD device may take the address 4 or 8 to expose only the functionalityof a standard DVD Playback Device. In this case, the recordingfunctionality will not be available or controllable via CEC.

A Recording Device with addresses 1, 2, or 9 (Recording Device) shallnot also take a Playback Device address as the playback functionality isalso included in the recorder functionality.

If a device has multiple instances of a particular functionality, itshould advertise only one instance. For instance, if a device hasmultiple tuners, it should only expose one for control via CEC. In thiscase, it is up to the device itself to manage multiple tuners.

A device shall advertise a function with a Logical Address, such as aTuner, only if it supports at least the mandatory for that function.

CEC 10.2.1 Logical Address Allocation

Note that a logical address should only be allocated when a device has avalid physical address (i.e., not F.F.F.F), at all other times a deviceshould take the Unregistered' logical address (15).

Only the device at physical address 0.0.0.0 may take logical addressTV(0). A TV at any other physical address shall take the Free Use' (14)address. If address 14 is already allocated it shall take theUnregistered' address (15).

Reserved addresses shall not be used at present and are reserved forfuture extensions to this specification.

Where more than one possible logical address is available for the givendevice type (e.g. Tuner 1, Tuner 2, etc.), an address allocationprocedure shall be carried out by a newly connected device. The devicetakes the first allocated address for that device type and sends a<Polling Message> to the same address (e.g. Tuner 1→Tuner 1). If the<Polling Message> is not acknowledged, then the device stops theprocedure and retains that address.

If the first address is acknowledged, then the device takes the nextaddress for that device type and repeats the process (e.g. Tuner 2→Tuner2). Again, if the message is not acknowledged, the device keeps thataddress.

This procedure continues until all possible type specific' addresseshave been checked; if no type specific' addresses are available, thedevice should take the unregistered address (15). Note that severalphysical devices might be sharing this address.

A device may lose its logical address when it is disconnected orswitched off. However, it may remember its previous logical address, sothat the next time it is reconnected or switched on, it can begin thepolling process at its previous logical address and try each otherallowable logical address in sequence before taking the unregisteredaddress. For example, if an STB that was previously allocated addressTuner 2 is reconnected, it would poll Tuner 2, Tuner 3, Tuner 4 andTuner 1 before taking the unregistered address.

If a device loses its physical address at any time (e.g. it isunplugged) then its logical address should be set to unregistered (15).

Now, FIG. 27 is a diagram illustrating “Table 5” in the HDMI Spec. 1.3a,i.e., a diagram illustrating logical addresses. Also, FIG. 28 is adiagram illustrating “FIG. 8” in the HDMI Spec. 1.3a, i.e., a diagramfor describing logical address Allocation.

On the other hand, with Ethernet (Registered Trademark), an IP addressof xx.xx.xx.xx is used, and the method thereof includes a methoddetermined by a DHCP server, a method wherein fixed addresses areprovided beforehand, and a method called AutoIP wherein an address isallocated to the self device dynamically. In general, with Ethernet(Registered Trademark), it takes time for this address allocation. Also,each of devices has frequently difficulty in being recognized dependingon a method for determining a fixed address.

That is to say, with a system including multiple devices to be connectedusing HDMI and Ethernet (Registered Trademark) together, it has beendifficult to determine an IP address to be used for Ethernet (RegisteredTrademark).

Therefore, with a system including multiple devices to be connectedusing HDMI and Ethernet (Registered Trademark) together, a method forsimply determining an IP address to be used for Ethernet (RegisteredTrademark) will be provided.

A Physical Address used for HDMI is indicated with A.B.C.D, and has 16bits in total of 4 bits×4, and simultaneously, represents connectiontopology between devices connected with HDMI.

On the other hand, an IP address used for Ethernet (RegisteredTrademark) has 64 bits in total of 16 bits X 4, and now, if we say thatan IP address used for Ethernet (Registered Trademark) is representedwith E.F.G.H for descriptive purposes, E, F, G, and H each have 16 bits.

A first method for determining an IP address used for Ethernet(Registered Trademark) has, such as shown in FIG. 29 for example, afundamental feature wherein an IP address is determined by allocating a16-bit value in total of A.B.C.D to the 16 bits of H. The values of E,F, and G are determined by the CEC Root that is A.B.C.D=0.0.0.0, andinformation of A.B.C.0 is transmitted over Ethernet (RegisteredTrademark). Each device determines the E.F.G.H of the self device basedon the information thereof and the self A.B.C.D. Thus, the address ofthe connection end having an HDMI terminal and Ethernet (RegisteredTrademark) terminal as a pair is determined.

In FIG. 29, the E.F.G.H of an IP address used for Ethernet (RegisteredTrademark), and A.B.C.D allocated to H are illustrated.

Also, for example, such as shown in FIG. 30, even in the case that anindependent Ethernet (Registered Trademark) terminal is providedseparately from a pair of the HDMI terminal and the Ethernet (RegisteredTrademark) terminal within the same device, the terminal thereof has noaddress of the A.B.C.D of an HDMI, but can determine the E.F.G.H of anIP address. 1.0.0.0 in FIG. 8-3, i.e., 1.0.0.0 in FIG. 26 is equivalentto this.

In FIG. 30, with a device 1001, an HDMI terminal 1002 and an Ethernet(Registered Trademark) terminal 1003 which make up a pair, an HDMIterminal 1004 and an Ethernet (Registered Trademark) terminal 1005 whichmake up a pair, and an Ethernet (Registered Trademark) terminal 1006 areprovided. Here, the Ethernet (Registered Trademark) terminal 1006 isindependently provided from the other terminals.

Also, multiple methods can be assumed wherein the CEC Root of which theA.B.C.D is 0.0.0.0 determines the values of E, F, and G. These are amethod using the values of fixed A, B, and C, a method for determiningwith reference to the address allocated from a DHCP server, and a methodusing AutoIP, and the like. Devices of which the values of E, F, and Gare the same can communicate freely within the same segment, butcommunication between devices of which the values thereof differ mayhave to have a router therebetween.

Further, as another solving means different from the first methoddescribed above, such as shown in FIG. 31 for example, there is a methodto take advantage of logical addresses (described as E here) in CEC. Alogical address in CEC has four bits, and these are allocated to thevalue of H. Also, the logical address 15 in CEC is used for Broadcast,and accordingly, the value may be converted into a value of 255.

FIG. 31 illustrates the E.F.G.H of an IP address used for Ethernet(Registered Trademark), and a logical address (E) to be allocated to thevalue of H.

Further, in this case, for example, such as shown in FIG. 32, in thecase that only an Ethernet (Registered Trademark) terminal isindependently provided separately from a pair of the HDMI terminal andthe Ethernet (Registered Trademark) terminal, the remaining 12 bits of Hof an IP address may be allocated to the independent terminal. Forexample, with a device of which the lower four bits are 1000b (8), theupper 12 bits of the IP address of the Ethernet (Registered Trademark)terminal of a pair of an HDMI terminal and an Ethernet (RegisteredTrademark) terminal is 000000000000b, and H is 8, but 000000000001b isallocated to the upper 12 bits of the IP address of the independentEthernet (Registered Trademark) terminal of the device thereof, andaccordingly, 0000000000011000b (24) becomes the value of H.

Description has been made so far regarding the address length of theavailable maximum width as an example, but an arrangement may be madewherein only 11 bits worth are used of the available 12 bits, withconsideration for future extensions and the like. Also, an offset may beadded to an address, or a logical address (E) may be allocated to aportion other than H.

As another third method different from the first method and the secondmethod described above, there is a method wherein an IP address isdetermined using a conventional method such as inquiring a DHCP server,or the like, and each of devices packetizes the correspondenceinformation as to the Physical Address and the logical address, andmutually exchanges this on CEC or Ethernet (Registered Trademark),thereby offering facility for an application to be used mutually betweenHDMI and Ethernet (Registered Trademark).

Also, FIG. 33 illustrates an IP address, a logical address, and aPhysical Address. Further, FIG. 34 illustrates three of IP address (1)through IP address (3), a logical address, and a Physical Address.

Further, with a device having a function for allocating multipleaddresses to a signal Ethernet (Registered Trademark) terminal, theabove first method, second method, or third method may be used together.In this case, the values of E, F, and G differ for each method. Also,with regard to an HDMI terminal and an Ethernet (Registered Trademark)terminal which make up a pair, a signal path for communicating anEthernet (Registered Trademark) signal is provided within an HDMI cable,whereby these may be handled as a single terminal and a single cable inan apparent manner.

As described above, with a system including multiple devices to beconnected using HDMI and Ethernet (Registered Trademark) together, an IPaddress to be used for Ethernet (Registered Trademark) can readily bedetermined.

Hereafter, the communication method described in the first embodimentwill be referred to as eHDMI connection. With the present embodiment, amethod for avoiding a loop will be described in the case of having theeHDMI connection coexist with common LAN connection.

An eHDMI connector and a LAN connector have to be mounted on a devicewhich can handle both of eHDMI and DLNA. With the eHDMI standard, adevice may be connected to a network via an eHDMI cable, but upon thedevice being connected to the network via the LAN connectorsimultaneously, the single device is connected to the network using twosystems, which causes a loop.

For example, such as shown in FIG. 35, let us say that a VIDEO (video)1101 and a BD/DVD Recorder (BD/DVD recorder) 1102 are connected to a DTV(Digital Television Receiver) 1103 via an eHDMI cable. Specifically, theVIDEO 1101 and an AVRack 1104 are connected with an eHDMI cable 1105,and the BD/DVD Recorder 1102 and the AVRack 1104 are connected with aneHDMI cable 1106. Also, the DTV 1103 is connected to the AVRack 1104with an eHDMI cable 1107.

Also, the eHDMI cables have a LAN cable function in addition to theconventional HDMI, and accordingly, the VIDEO 1101 and the BD/DVDRecorder 1102 are LAN-connected to a ROUTER (router) 1108 via the DTV1103. On the other hand, a common LAN connector has to be mounted on theVIDEO 1101, BD/DVD Recorder 1102, and the like assuming a case where auser who uses no eHDMI function performs DLNA connection. Upon the userconnecting a LAN cable to the LAN connector provided to each of theVIDEO 1101 and the BD/DVD Recorder 1102, and further connecting theopposite sides of the LAN cables thereof to the ROUTER 1108 in additionto eHDMI connection at the time of setting, the VIDEO 1101 and theBD/DVD Recorder 1102 are connected to the ROUTER 1108 with the twosystems of the eHDMI cable and the LAN cable, which causes a LOOP.Therefore, the user's attention has to be called by notes with a manual,and also some sort of evasive measure has to be taken on the main unitside of the device. That is to say, in the case of having eHDMIconnection coexist with common LAN connection, there is a possibilitythat a LOOP may be caused.

Therefore, as a method for avoiding such a LOOP, a software-based methodand a hardware-based method will be described below.

First, a menu is displayed on a device which can handle both of eHDMIand DLNA, and an eHDMI mode ON/OFF button is provided on the menuthereof. This eHDMI mode ON/OFF button is operated by the user, therebyswitching which of the LAN connector and the eHDMI connector provided tothe device should be activated. Description will be made below regardingswitching processing that is processing for the device executingswitching of these LAN connector and eHDMI connector, with reference tothe flowchart in FIG. 36.

In step S301, the device displays the menu. The eHDMI mode ON/OFF buttonis displayed on this menu, and the user operates the device, whereby oneof the ON state or OFF state of the eHDMI mode for switching the activeconnector can be selected by this eHDMI mode ON/OFF button.

In step S302, the device determines whether or not the ON state of theeHDMI mode has been specified. Upon determining in step S302 that the ONstate has been specified, in step S303 the device turns on the eHDMImode, and the switching processing ends. That is to say, the deviceactivates the eHDMI connector provided to the self device, andinactivates the LAN connector. Thus, only the eHDMI connector isactivated, and occurrence of a LOOP can be avoided.

On the other hand, in the case that determination is made in step S302that the ON state has not been specified, in step S304 the device turnsoff the eHDMI mode, and the switching processing ends. That is to say,the device inactivates the eHDMI connector provided to the self device,and activates the LAN connector. The eHDMI connector activated herefunctions as HDMI. Thus, only the LAN connector is activated, andoccurrence of a LOOP can be avoided.

Thus, the menu is displayed, and the user is allowed to select so as toactivate any one connector of the eHDMI connector and the LAN connector,whereby a LOOP can be readily avoided.

Next, a hardware-based method for avoiding a LOOP will be described.

In such a case, for example, only eHDMI is mounted on the device. Also,in the case that this device directly connects to DLNA without passingthrough eHDMI, i.e., in the case of carrying out LAN connection toanother device without passing through the eHDMI cable, a conversionadaptor 1131 shown in FIG. 37 is used, for example.

The conversion adaptor 1131 is an adaptor for separating eHDMI into LANand HDMI, or combining LAN and HDMI to obtain eHDMI. With thisconversion adaptor 1131, a terminal 1132 for eHDMI, a terminal 1133 forLAN, and a terminal 1134 for HDMI are provided. Such a conversionadaptor 1131 is connected to a device on which only eHDMI is mounted,whereby LAN connection can be carried out to another device withoutpassing through an eHDMI cable.

Also, another hardware-based method for avoiding a LOOP may be used, forexample, such as shown in FIG. 38, wherein a hard switch is provided tothe device, and connection to the eHDMI connector and connection to theLAN connector is switched.

In FIG. 38, with the device, a network controller 1161, an HDMIcontroller 1162, an eHDMI controller 1163, a switch 1164, an HDMIconnector (eHDMI connector) 1165, and a LAN connector 1166 are provided.

The HDMI controller 1162 is connected to the eHDMI controller 1163, andthe eHDMI controller 1163 is connected to the HDMI connector 1165.Further, the switch 1164 is connected to the network controller 1161,and the switch 1164 is switched to connect to one of the eHDMIcontroller 1163 and the LAN connector 1166.

Here, upon the switch 1164 being connected to the eHDMI controller 1163,the network controller 1161 is connected to the HDMI connector 1165 viathe eHDMI controller 1163. Also, upon the switch 1164 being connected tothe LAN connector 1166, the network controller 1161 is connected to theLAN connector 1166. Thus, connection is switched to the HDMI connector1165 or LAN connector 1166 by the switch 1164, whereby a LOOP canreadily be avoided.

Further, another hardware-based method for avoiding a LOOP may be used,for example, such as shown in FIG. 39, wherein the LAN connector 1191and the HDMI connector (eHDMI connector) 1192 are provided closely tothe device, and only one of the connectors is allowed to be connected.That is to say, only one of the LAN connector 1191 and the HDMIconnector 1192 is connected to another device via a cable or the like.

Further, another hardware-based method for avoiding a LOOP may be usedwherein two network control chips for eHDMI connectors and for LANconnectors are mounted on the device.

In such a case, for example, such as shown in FIG. 40, with the device,a LAN connector 1211, an HDMI connector (eHDMI connector) 1212, anetwork controller 1213, an eHDMI controller 1214, an HDMI controller1215, and a network controller 1216 are provided.

Here, the LAN connector 1211 is connected to the network controller1213. Also, the HDMI connector 1212 is connected to the eHDMI controller1214, and the HDMI controller 1215 and the network controller 1216 areconnected to the eHDMI controller 1214.

Thus, the network controller 1213 for the LAN connector 1211, and thenetwork controller 1216 for the HDMI connector 1212 are provide to thedevice, whereby a LOOP can readily be avoided.

The invention claimed is:
 1. A communication method for a transmissiondevice having a transmitting unit for transmitting video data and audiodata to an external device by a differential signal via a HighDefinition Multimedia Interface (HDMI), the method comprising the stepsof: communicating with the external device using a communication unitfor performing communication by a differential signal via abi-directional communication path including a reserved line and a HotPlug Detect (HPD) line of an HDMI cable, the communication unit having atransmitter and a receiver; receiving a notification of a connectionstate from the external device by a DC bias potential of the HPD line;and receiving a signal obtained by subtracting a transmission signalinput to the transmitter from an output signal output from the receiver.